Section 8: Alterations in the Skin

INTRODUCTION

The challenge of examining the skin lies in distinguishing normal from abnormal findings, distinguishing significant findings from trivial ones, and integrating pertinent signs and symptoms into an appropriate differential diagnosis. The fact that the largest organ in the body is visible is both an advantage and a disadvantage to those who examine it. It is advantageous because no special instrumentation is necessary and because the skin can be biopsied with little morbidity. However, the casual observer can be misled by a variety of stimuli and overlook important, subtle signs of skin or systemic disease. For instance, the sometimes minor differences in color and shape that distinguish a melanoma (Fig. 56-1) from a benign nevomelanocytic nevus (Fig. 56-2) can be difficult to recognize. A variety of descriptive terms have been developed that characterize cutaneous lesions (Tables 56-1, 56-2, and 56-3; Fig. 56-3), thereby aiding in their interpretation and in the formulation of a differential diagnosis (Table 56-4). For example, the finding of scaling papules, which are present in psoriasis or atopic dermatitis, places the patient in a different diagnostic category than would hemorrhagic papules, which may indicate vasculitis or sepsis (Figs. 56-4 and 56-5, respectively). It is also important to differentiate primary from secondary skin lesions. If the examiner focuses on linear erosions overlying an area of erythema and scaling, he or she may incorrectly assume that the erosion is the primary lesion and that the redness and scale are secondary, whereas the correct interpretation would be that the patient has a pruritic eczematous dermatitis with erosions caused by scratching.

DIAGNOSTIC TECHNIQUES

Many skin diseases can be diagnosed on the basis of gross clinical appearance, but sometimes relatively simple diagnostic procedures can yield valuable information. In most instances, they can be performed at the bedside with a minimum of equipment.

Skin Biopsy

A skin biopsy is a straightforward minor surgical procedure; however, it is important to biopsy a lesion that is most likely to yield diagnostic findings. This decision may require expertise in skin diseases and knowledge of superficial anatomic structures in selected areas of the body. In this procedure, a small area of skin is anesthetized with 1% lidocaine with or without epinephrine. The skin lesion in question can be excised or saucerized with a scalpel or removed by punch biopsy. In the latter technique, a punch is pressed against the surface of the skin and rotated with downward pressure until it penetrates to the subcutaneous tissue. The circular biopsy is then lifted with forceps, and the bottom is cut with iris scissors. Biopsy sites may or may not need suture closure, depending on size and location.

KOH Preparation

A potassium hydroxide (KOH) preparation is performed on scaling skin lesions where a fungal infection is suspected. The edge of such a lesion is scraped gently with a no. 15 scalpel blade. The removed scale is collected on a glass microscope slide, treated with 1 or 2 drops of a solution of 10–20% KOH, and placement of a cover slip. KOH dissolves keratin and allows easier visualization of fungal elements. Brief heating of the slide accelerates dissolution of keratin. When the preparation is viewed under the microscope, the refractile hyphae are seen more easily when the light intensity is reduced and the condenser is lowered. This technique can be used to identify hyphae in dermatophyte infections, pseudohyphae and budding yeasts in Candida infections, and “spaghetti and meatballs” yeast forms in tinea versicolor. The same sampling technique can be used to obtain scale for culture of selected pathogenic organisms.

Tzanck Smear

A Tzanck smear is a cytologic technique most often used in the diagnosis of herpesvirus infections (herpes simplex virus [HSV] or varicella-zoster virus [VZV]) (see Figs. 193-1 and 193-3). An early vesicle, not a pustule or crusted lesion, is unroofed, and the base of the lesion is scraped gently with a scalpel blade. The material is placed on a glass slide, air-dried, and stained with Giemsa or Wright’s stain. Multinucleated epithelial giant cells suggest the presence of HSV or VZV; culture, immunofluorescence microscopy, or genetic testing must be performed to identify the specific virus.

Diascopy

Diascopy is designed to assess whether a skin lesion will blanch with pressure as, for example, in determining whether a red lesion is hemorrhagic or simply blood-filled. Urticaria (Fig. 56-11) will blanch with pressure, whereas a purpuric lesion caused by necrotizing vasculitis (Fig. 56-4) will not. Diascopy is performed by pressing a microscope slide or magnifying lens against a lesion and noting the amount of blanching that occurs. Granulomas often have an opaque to transparent, brown-pink “apple jelly” appearance on diascopy.

Dermoscopy

Dermoscopy is a noninvasive method of examining the skin surface that uses a high-quality magnifying lens and a specialized light source (i.e., a dermatoscope). Dermoscopy identifies skin structures, colors, and patterns that are not visible to the naked eye. It is particularly useful in the evaluation of pigmented skin lesions.

Wood’s Light

A Wood’s lamp generates 360-nm ultraviolet (“black”) light that can be used to aid the evaluation of certain skin disorders. For example, a Wood’s lamp will cause erythrasma (a superficial, intertriginous infection caused by Corynebacterium minutissimum) to show a characteristic coral pink color, and wounds colonized by Pseudomonas will appear pale blue. Tinea capitis caused by certain dermatophytes (e.g., Microsporum canis or M. audouinii) exhibits a yellow fluorescence. Pigmented lesions of the epidermis such as freckles are accentuated, while dermal pigment such as postinflammatory hyperpigmentation fades under a Wood’s light. Vitiligo (Fig. 56-12) appears totally white under a Wood’s lamp, and previously unsuspected areas of involvement often become apparent. A Wood’s lamp may also aid in the demonstration of tinea versicolor, detection of sites of depigmentation within and/or surrounding melanomas, and recognition of ash leaf spots in patients with tuberous sclerosis.

Patch Tests

Patch testing is designed to document sensitivity to a specific antigen. In this procedure, a battery of suspected allergens is applied to the patient’s back under occlusive dressings and allowed to remain in contact with the skin for 48 h. The dressings are removed, and the area is examined for evidence of delayed hypersensitivity reactions (e.g., erythema, edema, or papulovesicles). This test is best performed by physicians with special expertise in patch testing and is often helpful in the evaluation of patients with chronic dermatitis.

FURTHER READING

ECZEMA AND DERMATITIS

Eczema is a type of dermatitis, and these terms are often used synonymously (e.g., atopic eczema or atopic dermatitis [AD]). Eczema is a reaction pattern that presents with variable clinical findings and the common histologic finding of spongiosis (intercellular edema of the epidermis). Eczema is the final common expression for a number of disorders, including those discussed in the following sections. Primary lesions may include erythematous macules, papules, and vesicles, which can coalesce to form patches and plaques. In severe eczema, secondary lesions from infection or excoriation, marked by weeping and crusting, may predominate. In chronic eczematous conditions, lichenification (cutaneous hypertrophy and accentuation of normal skin markings) may alter the characteristic appearance of eczema.

ATOPIC DERMATITIS

AD is the cutaneous expression of the atopic state, characterized by a family history of asthma, allergic rhinitis, or eczema. The prevalence of AD is increasing worldwide. Some of its features are shown in Table 57-1. The etiology of AD is only partially defined, but there is a clear genetic predisposition. When both parents are affected by AD, >80% of their children manifest the disease. When only one parent is affected, the prevalence drops to slightly >50%. A characteristic defect in AD that contributes to the pathophysiology is an impaired epidermal barrier. In many patients, a mutation in the gene encoding filaggrin, a structural protein in the stratum corneum, is responsible. Patients with AD may display a variety of immunoregulatory abnormalities, including increased IgE synthesis; increased serum IgE levels; and impaired, delayed-type hypersensitivity reactions.

The clinical presentation often varies with age. Half of patients with AD present within the first year of life, and 80% present by 5 years of age. About 80% ultimately coexpress allergic rhinitis or asthma. The infantile pattern is characterized by weeping inflammatory patches and crusted plaques on the face, neck, and extensor surfaces. The childhood and adolescent patterns are typified by dermatitis of flexural skin, particularly in the antecubital and popliteal fossae (Fig. 57-1). AD may resolve spontaneously, but approximately 40% of all individuals affected as children will have dermatitis in adult life. The distribution of lesions in adults may be similar to those seen in childhood; however, adults frequently have localized disease manifesting as lichen simplex chronicus or hand eczema (see below). In patients with localized disease, AD may be suspected because of a typical personal or family history or the presence of cutaneous stigmata of AD such as perioral pallor, an extra fold of skin beneath the lower eyelid (Dennie-Morgan folds), increased palmar skin markings, and an increased incidence of cutaneous infections, particularly with Staphylococcus aureus. Regardless of other manifestations, pruritus is a prominent characteristic of AD in all age groups and is exacerbated by dry skin. Many of the cutaneous findings in affected patients, such as lichenification, are secondary to rubbing and scratching.

LICHEN SIMPLEX CHRONICUS

Lichen simplex chronicus may represent the end stage of a variety of pruritic and eczematous disorders, including AD. It consists of a circumscribed plaque or plaques of lichenified skin due to chronic scratching or rubbing. Common areas involved include the posterior nuchal region, dorsum of the feet, and ankles. Treatment of lichen simplex chronicus centers on breaking the cycle of chronic itching and scratching. High-potency topical glucocorticoids are helpful in most cases, but, in recalcitrant cases, application of topical glucocorticoids under occlusion or intralesional injection of glucocorticoids may be required.

CONTACT DERMATITIS

Contact dermatitis is an inflammatory skin process caused by an exogenous agent or agents that directly or indirectly injure the skin. In irritant contact dermatitis (ICD), this injury is caused by an inherent characteristic of a compound—for example, a concentrated acid or base. Agents that cause allergic contact dermatitis (ACD) induce an antigen-specific immune response (e.g., poison ivy dermatitis). The clinical lesions of contact dermatitis may be acute (wet and edematous) or chronic (dry, thickened, and scaly), depending on the persistence of the insult (see Chap. 56, Fig. 56-10).

Irritant Contact Dermatitis

ICD is generally well demarcated and often localized to areas of thin skin (eyelids, intertriginous areas) or areas where the irritant was occluded. Lesions may range from minimal skin erythema to areas of marked edema, vesicles, and ulcers. Prior exposure to the offending agent is not necessary, and the reaction develops in minutes to a few hours. Chronic low-grade irritant dermatitis is the most common type of ICD, and the most common area of involvement is the hands (see below). The most common irritants encountered are chronic wet work, soaps, and detergents. Treatment should be directed toward the avoidance of irritants and the use of protective gloves or clothing.

Allergic Contact Dermatitis

ACD is a manifestation of delayed-type hypersensitivity mediated by memory T lymphocytes in the skin. Prior exposure to the offending agent is necessary to develop the hypersensitivity reaction, which may take as little as 12 h or as long as 72 h to develop. The most common cause of ACD is exposure to plants, especially to members of the family Anacardiaceae, including the genus Toxicodendron. Poison ivy, poison oak, and poison sumac are members of this genus and cause an allergic reaction marked by erythema, vesiculation, and severe pruritus. The eruption is often linear or angular, corresponding to areas where plants have touched the skin. The sensitizing antigen common to these plants is urushiol, an oleoresin containing the active ingredient pentadecylcatechol. The oleoresin may adhere to skin, clothing, tools, and pets, and contaminated articles may cause dermatitis even after prolonged storage. Blister fluid does not contain urushiol and is not capable of inducing skin eruption in exposed subjects.

HAND ECZEMA

Hand eczema is a very common, chronic skin disorder in which both exogenous and endogenous factors play important roles. It may be associated with other cutaneous disorders such as AD, and contact with various agents may be involved. Hand eczema represents a large proportion of cases of occupation-associated skin disease. Chronic, excessive exposure to water and detergents, harsh chemicals, or allergens may initiate or aggravate this disorder. It may present with dryness and cracking of the skin of the hands as well as with variable amounts of erythema and edema. Often, the dermatitis will begin under rings, where water and irritants are trapped. Dyshidrotic eczema, a variant of hand eczema, presents with multiple, intensely pruritic, small papules and vesicles on the thenar and hypothenar eminences and the sides of the fingers (Fig. 57-2). Lesions tend to occur in crops that slowly form crusts and then heal.

The evaluation of a patient with hand eczema should include an assessment of potential occupation-associated exposures. The history should be directed to identifying possible irritant or allergen exposures.

NUMMULAR ECZEMA

Nummular eczema is characterized by circular or oval “coinlike” lesions, beginning as small edematous papules that become crusted and scaly. The etiology of nummular eczema is unknown, but dry skin is a contributing factor. Common locations are the trunk or the extensor surfaces of the extremities, particularly on the pretibial areas or dorsum of the hands. Nummular eczema occurs more frequently in men and is most common in middle age. The treatment of nummular eczema is similar to that for AD.

ASTEATOTIC ECZEMA

Asteatotic eczema, also known as xerotic eczema or “winter itch,” is a mildly inflammatory dermatitis that develops in areas of extremely dry skin, especially during the dry winter months. Clinically, there may be considerable overlap with nummular eczema. This form of eczema accounts for many physician visits because of the associated pruritus. Fine cracks and scale, with or without erythema, characteristically develop in areas of dry skin, especially on the anterior surfaces of the lower extremities in elderly patients. Asteatotic eczema responds well to topical moisturizers and the avoidance of cutaneous irritants. Overbathing and the use of harsh soaps exacerbate asteatotic eczema.

STASIS DERMATITIS AND STASIS ULCERATION

Stasis dermatitis develops on the lower extremities secondary to venous incompetence and chronic edema. Patients may give a history of deep venous thrombosis and may have evidence of vein removal or varicose veins. Early findings in stasis dermatitis consist of mild erythema and scaling associated with pruritus. The typical initial site of involvement is the medial aspect of the ankle, often over a distended vein (Fig. 57-3).

Stasis dermatitis may become acutely inflamed, with crusting and exudate. In this state, it is easily confused with cellulitis. Of note, symmetrical and bilateral involvement is more likely stasis dermatitis, whereas unilateral involvement may represent cellulitis. Chronic stasis dermatitis is often associated with dermal fibrosis that is recognized clinically as brawny edema of the skin. As the disorder progresses, the dermatitis becomes progressively pigmented due to chronic erythrocyte extravasation leading to cutaneous hemosiderin deposition. Stasis dermatitis may be complicated by secondary infection and contact dermatitis. Severe stasis dermatitis may precede the development of stasis ulcers.

SEBORRHEIC DERMATITIS

Seborrheic dermatitis is a common, chronic disorder characterized by greasy scales overlying erythematous patches or plaques. Induration and scale are generally less prominent than in psoriasis, but clinical overlap exists between these diseases (“sebopsoriasis”). The most common location is in the scalp, where it may be recognized as severe dandruff. On the face, seborrheic dermatitis affects the eyebrows, eyelids, glabella, and nasolabial folds (Fig. 57-4). Scaling of the external auditory canal is common in seborrheic dermatitis. In addition, the postauricular areas often become macerated and tender. Seborrheic dermatitis may also develop in the central chest, axilla, groin, submammary folds, and gluteal cleft. Rarely, it may cause widespread generalized dermatitis. Pruritus is variable.

Seborrheic dermatitis may be evident within the first few weeks of life, and within this context, it typically occurs in the scalp (“cradle cap”), face, or groin. It is rarely seen in children beyond infancy but becomes evident again during adolescent and adult life. Although it is frequently seen in patients with Parkinson’s disease, in those who have had cerebrovascular accidents, and in those with HIV infection, the overwhelming majority of individuals with seborrheic dermatitis have no underlying disorder.

PAPULOSQUAMOUS DISORDERS

(TABLE 57-2)

PSORIASIS

Psoriasis is one of the most common dermatologic diseases, affecting up to 2% of the world’s population. It is an immune-mediated disease clinically characterized by erythematous, sharply demarcated papules and rounded plaques covered by silvery micaceous scale. The skin lesions of psoriasis are variably pruritic. Traumatized areas often develop lesions of psoriasis (the Koebner or isomorphic phenomenon). In addition, other external factors may exacerbate psoriasis, including infections, stress, and medications (lithium, beta blockers, and antimalarial drugs).

The most common variety of psoriasis is called plaque-type. Patients with plaque-type psoriasis have stable, slowly enlarging plaques, which remain basically unchanged for long periods of time. The most commonly involved areas are the elbows, knees, gluteal cleft, and scalp. Involvement tends to be symmetric. Plaque psoriasis generally develops slowly and runs an indolent course. It rarely remits spontaneously. Inverse psoriasis affects the intertriginous regions, including the axilla, groin, submammary region, and navel; it also tends to affect the scalp, palms, and soles. The individual lesions are sharply demarcated plaques (see Chap. 56, Fig. 56-7), but they may be moist and without scale due to their locations.

Guttate psoriasis (eruptive psoriasis) is most common in children and young adults. It develops acutely in individuals without psoriasis or in those with chronic plaque psoriasis. Patients present with many small erythematous, scaling papules, frequently after upper respiratory tract infection with β-hemolytic streptococci. The differential diagnosis should include pityriasis rosea and secondary syphilis.

In pustular psoriasis, patients may have disease localized to the palms and soles, or the disease may be generalized. Regardless of the extent of disease, the skin is erythematous, with pustules and variable scale. Localized to the palms and soles, it is easily confused with dishydrotic eczema. When it is generalized, episodes are characterized by fever (39°–40°C [102.2°–104.0°F]) lasting several days, an accompanying generalized eruption of sterile pustules, and a background of intense erythema; patients may become erythrodermic. Episodes of fever and pustules are recurrent. Local irritants, pregnancy, medications, infections, and systemic glucocorticoid withdrawal can precipitate this form of psoriasis. Oral retinoids are the treatment of choice in nonpregnant patients.

Fingernail involvement, appearing as punctate pitting, onycholysis, nail thickening, or subungual hyperkeratosis, may be a clue to the diagnosis of psoriasis when the clinical presentation is not classic.

According to the National Psoriasis Foundation, up to 30% of patients with psoriasis have psoriatic arthritis (PsA). It develops most commonly between the ages of 30 and 50 years. There are five subtypes of PsA: symmetric PsA, asymmetric PsA, distal PsA, spondylitis, and arthritis mutilans. Approximately 50% of PsA is classified as symmetric, which may resemble rheumatoid arthritis. Asymmetric arthritis comprises about 35% of cases. It can involve any joint and may present as “sausage digits.” Distal PsA is the classic form; however, it occurs in only about 5% of patients with PsA. It can involve fingers and toes; fingernails and toenails are often dystrophic, including nail pitting. Spondylitis also occurs in ~5% of patients with PsA. Arthritis mutilans is severe and deforming and affects primarily the small joints of the hands and feet. It accounts for fewer than 5% of PsA cases.

An increased risk of metabolic syndrome, including increased morbidity and mortality from cardiovascular events, has been demonstrated in psoriasis patients. Appropriate screening tests should be performed. The etiology of psoriasis is still poorly understood, but there is clearly a genetic component to the disease. In various studies, 30–50% of patients with psoriasis report a positive family history. Psoriatic lesions contain infiltrates of activated T cells that are thought to elaborate cytokines responsible for keratinocyte hyperproliferation, which results in the characteristic clinical findings. Agents inhibiting T-cell activation, clonal expansion, or release of proinflammatory cytokines are often effective for the treatment of severe psoriasis (see below).

LICHEN PLANUS

Lichen planus (LP) is a papulosquamous disorder that may affect the skin, scalp, nails, and mucous membranes. The primary cutaneous lesions are pruritic, polygonal, flat-topped, violaceous papules. Close examination of the surface of these papules often reveals a network of gray lines (Wickham’s striae). The skin lesions may occur anywhere but have a predilection for the wrists, shins, lower back, and genitalia (Fig. 57-5). Involvement of the scalp (lichen planopilaris) may lead to scarring alopecia, and nail involvement may lead to permanent deformity or loss of fingernails and toenails. LP commonly involves mucous membranes, particularly the buccal mucosa, where it can present on a spectrum ranging from a mild, white, reticulate eruption of the mucosa to a severe, erosive stomatitis. Erosive stomatitis may persist for years and may be linked to an increased risk of oral squamous cell carcinoma. Cutaneous eruptions clinically resembling LP have been observed after administration of numerous drugs, including thiazide diuretics, gold, antimalarial agents, penicillamine, and phenothiazines, and in patients with skin lesions of chronic graft-versus-host disease. In addition, LP may be associated with hepatitis C infection. The course of LP is variable, but most patients have spontaneous remissions 6 months to 2 years after the onset of disease. Topical glucocorticoids are the mainstay of therapy.

PITYRIASIS ROSEA

Pityriasis rosea (PR) is a papulosquamous eruption of unknown etiology occurring more commonly in the spring and fall. Its first manifestation is the development of a 2- to 6-cm annular lesion (the herald patch). This is followed in a few days to a few weeks by the appearance of many smaller annular or papular lesions with a predilection to occur on the trunk (Fig. 57-6). The lesions are generally oval, with their long axis parallel to the skinfold lines. Individual lesions may range in color from red to brown and have a trailing scale. PR shares many clinical features with the eruption of secondary syphilis, but palm and sole lesions are extremely rare in PR and common in secondary syphilis. The eruption tends to be moderately pruritic and lasts 3–8 weeks. Treatment is directed at alleviating pruritus and consists of oral antihistamines; mid-potency topical glucocorticoids; and, in some cases, UVB phototherapy.

CUTANEOUS INFECTIONS

(TABLE 57-5)

IMPETIGO, ECTHYMA, AND FURUNCULOSIS

Impetigo is a common superficial bacterial infection of skin caused most often by S. aureus (Chap. 147) and in some cases by group A β-hemolytic streptococci (Chap. 148). The primary lesion is a superficial pustule that ruptures and forms a characteristic yellow-brown honey-colored crust (see Chap. 148, Fig. 148-3). Lesions may occur on normal skin (primary infection) or in areas already affected by another skin disease (secondary infection). Lesions caused by staphylococci may be tense, clear bullae, and this less common form of the disease is called bullous impetigo. Blisters are caused by the production of exfoliative toxin by S. aureus phage type II. This is the same toxin responsible for staphylococcal scalded-skin syndrome, often resulting in dramatic loss of the superficial epidermis due to blistering. The latter syndrome is much more common in children than in adults; however, it should be considered along with toxic epidermal necrolysis and severe drug eruptions in patients with widespread blistering of the skin. Ecthyma is a deep nonbullous variant of impetigo that causes punched-out ulcerative lesions. It is more often caused by a primary or secondary infection with Streptococcus pyogenes. Ecthyma is a deeper infection than typical impetigo and resolves with scars. Treatment of both ecthyma and impetigo involves gentle debridement of adherent crusts, facilitated by using soaks and topical antibiotics in conjunction with appropriate oral antibiotics.

Furunculosis is also caused by S. aureus, and this disorder has gained prominence in the past few decades because of CA-MRSA. A furuncle, or boil, is a painful, erythematous nodule that can occur on any cutaneous surface. The lesions may be solitary but are most often multiple. Patients frequently believe they have been bitten by spiders or insects. Family members or close contacts may also be affected. Furuncles can rupture and drain spontaneously or may need incision and drainage, which may be adequate therapy for small solitary furuncles without cellulitis or systemic symptoms. Whenever possible, lesional material should be sent for culture. Current recommendations for methicillin-sensitive infections are β-lactam antibiotics. Therapy for CA-MRSA is discussed previously (see “Atopic Dermatitis”). Warm compresses and nasal mupirocin are helpful therapeutic additions. Severe infections may require IV antibiotics.

ERYSIPELAS AND CELLULITIS

See Chap. 129.

DERMATOPHYTOSIS

Dermatophytes are fungi that infect skin, hair, and nails and include members of the genera Trichophyton, Microsporum, and Epidermophyton (Chap. 219). Tinea corporis, or infection of the relatively hairless skin of the body (glabrous skin), may have a variable appearance depending on the extent of the associated inflammatory reaction. Typical infections consist of erythematous, scaly plaques, with an annular appearance that accounts for the common name “ringworm.” Deep inflammatory nodules or granulomas occur in some infections, most often those inappropriately treated with mid- to high-potency topical glucocorticoids. Involvement of the groin (tinea cruris) is more common in males than in females. It presents as a scaling, erythematous eruption sparing the scrotum. Infection of the foot (tinea pedis) is the most common dermatophyte infection and is often chronic; it is characterized by variable erythema, edema, scaling, pruritus, and occasionally vesiculation. The infection may be widespread or localized but generally involves the web space between the fourth and fifth toes. Infection of the nails (tinea unguium or onychomycosis) occurs in many patients with tinea pedis and is characterized by opacified, thickened nails and subungual debris. The distal-lateral variant is most common. Proximal subungual onychomycosis may be a marker for HIV infection or other immunocompromised states. Dermatophyte infection of the scalp (tinea capitis) continues to be common, particularly affecting inner-city children but also affecting immunocompromised adults. The predominant organism is Trichophyton tonsurans, which can produce a relatively noninflammatory infection with mild scale and hair loss that is diffuse or localized. T. tonsurans and Microsporum canis can also cause a markedly inflammatory dermatosis with edema and nodules. This latter presentation is a kerion.

The diagnosis of tinea can be made from skin scrapings, nail scrapings, or hair by culture or direct microscopic examination with KOH. Nail clippings may be sent for histologic examination with periodic acid–Schiff (PAS) stain.

TINEA (PITYRIASIS) VERSICOLOR

Tinea versicolor is caused by a nondermatophytic, dimorphic fungus, Malassezia furfur, a normal inhabitant of the skin. The expression of infection is promoted by heat and humidity. The typical lesions consist of oval scaly macules, papules, and patches concentrated on the chest, shoulders, and back but only rarely on the face or distal extremities. On dark skin, the lesions often appear as hypopigmented areas, whereas on light skin, they are slightly erythematous or hyperpigmented. A KOH preparation from scaling lesions will demonstrate a confluence of short hyphae and round spores (“spaghetti and meatballs”). Lotions or shampoos containing sulfur, salicylic acid, or selenium sulfide are the treatments of choice and will clear the infection if used daily for 1–2 weeks and then weekly thereafter. These preparations are irritating if left on the skin for >10 min; thus, they should be washed off completely. Treatment with some oral antifungal agents is also effective, but they do not provide lasting results and are not FDA approved for this indication.

CANDIDIASIS

Candidiasis is a fungal infection caused by a related group of yeasts whose manifestations may be localized to the skin and mucous membranes or, rarely, may be systemic and life-threatening (Chap. 216). The causative organism is usually Candida albicans. These organisms are normal saprophytic inhabitants of the gastrointestinal tract but may overgrow due to broad-spectrum antibiotic therapy, diabetes mellitus, or immunosuppression and cause disease. Candidiasis is a very common infection in HIV-infected individuals (Chap. 202). The oral cavity is commonly involved. Lesions may occur on the tongue or buccal mucosa (thrush) and appear as white plaques. Fissured, macerated lesions at the corners of the mouth (perlèche) are often seen in individuals with poorly fitting dentures and may also be associated with candidal infection. In addition, candidal infections have an affinity for sites that are chronically wet and macerated, including the skin around nails (onycholysis and paronychia), and in intertriginous areas. Intertriginous lesions are characteristically edematous, erythematous, and scaly, with scattered “satellite pustules.” In males, there is often involvement of the penis and scrotum as well as the inner aspect of the thighs. In contrast to dermatophyte infections, candidal infections are frequently painful and accompanied by a marked inflammatory response. Diagnosis of candidal infection is based on the clinical pattern and demonstration of yeast on KOH preparation or culture.

WARTS

Warts are cutaneous neoplasms caused by papillomaviruses. More than 100 different human papillomaviruses (HPVs) have been described. A typical wart, verruca vulgaris, is sessile, dome-shaped, and usually about a centimeter in diameter. Its surface is hyperkeratotic, consisting of many small filamentous projections. HPV also causes typical plantar warts, flat warts (verruca plana), and filiform warts. Plantar warts are endophytic and are covered by thick keratin. Paring of the wart will generally reveal a central core of keratinized debris and punctate bleeding points. Filiform warts are commonly seen on the face, neck, and skinfolds and present as papillomatous lesions on a narrow base. Flat warts are only slightly elevated and have a velvety, nonverrucous surface. They have a propensity for the face, arms, and legs, and are often spread by shaving.

Genital warts begin as small papillomas that may grow to form large, fungating lesions. In women, they may involve the labia, perineum, or perianal skin. In addition, the mucosa of the vagina, urethra, and anus can be involved as well as the cervical epithelium. In men, the lesions often occur initially in the coronal sulcus but may be seen on the shaft of the penis, the scrotum, or the perianal skin or in the urethra.

Appreciable evidence has accumulated indicating that HPV plays a role in the development of neoplasia of the uterine cervix and anogenital skin (Chap. 89). HPV types 16 and 18 have been most intensely studied and are the major risk factors for intraepithelial neoplasia and squamous cell carcinoma of the cervix, anus, vulva, and penis. The risk is higher among patients immunosuppressed after solid organ transplantation and among those infected with HIV. Recent evidence also implicates other HPV types. Histologic examination of biopsied samples from affected sites may reveal changes associated with typical warts and/or features typical of intraepidermal carcinoma (Bowen’s disease). Squamous cell carcinomas associated with HPV infections have also been observed in extragenital skin (Chap. 76), most commonly in patients immunosuppressed after organ transplantation. Patients on long-term immunosuppression should be monitored for the development of squamous cell carcinoma and other cutaneous malignancies.

HERPES SIMPLEX

See Chap. 192.

HERPES ZOSTER

See Chap. 193.

ACNE

ACNE VULGARIS

Acne vulgaris is a self-limited disorder primarily of teenagers and young adults, although perhaps 10–20% of adults may continue to experience some form of the disorder. The permissive factor for the expression of the disease in adolescence is the increase in sebum production by sebaceous glands with puberty. Small cysts, called comedones, form in hair follicles due to blockage of the follicular orifice by retention of keratinous material and sebum. The activity of bacteria (Cutibacterium acnes) within the comedones releases free fatty acids from sebum, causes inflammation within the cyst, and results in rupture of the cyst wall. An inflammatory foreign-body reaction develops as result of extrusion of oily and keratinous debris from the cyst.

The clinical hallmark of acne vulgaris is the comedone, which may be closed (whitehead) or open (blackhead). Closed comedones appear as 1- to 2-mm pebbly white papules, which are accentuated when the skin is stretched. They are the precursors of inflammatory lesions of acne vulgaris. The contents of closed comedones are not easily expressed. Open comedones, which rarely result in inflammatory acne lesions, have a dilated follicular orifice and are filled with easily expressible oxidized, darkened, oily debris. Comedones are usually accompanied by inflammatory lesions: papules, pustules, or nodules.

The earliest lesions seen in adolescence are generally mildly inflamed or noninflammatory comedones on the forehead. Subsequently, more typical inflammatory lesions develop on the cheeks, nose, and chin (Fig. 57-7). The most common location for acne is the face, but involvement of the chest and back is common. Most disease remains mild and does not lead to scarring. A small number of patients develop large inflammatory cysts and nodules, which may drain and result in significant scarring. Regardless of the severity, acne may affect a patient’s quality of life. With adequate treatment, this effect may be transient. In the case of severe, scarring acne, the effects can be permanent and profound. Early therapeutic intervention in severe acne is essential.

Exogenous and endogenous factors can alter the expression of acne vulgaris. Friction and trauma (from headbands or chin straps of athletic helmets), application of comedogenic topical agents (cosmetics or hair preparations), or chronic topical exposure to certain industrial compounds may elicit or aggravate acne. Glucocorticoids, topical or systemic, may also elicit acne. Other systemic medications such as progestin-only contraception, lithium, isoniazid, androgenic steroids, halogens, phenytoin, and phenobarbital may produce acneiform eruptions or aggravate preexisting acne. Genetic factors and polycystic ovary disease may also play a role.

ACNE ROSACEA

Acne rosacea, commonly referred to simply as rosacea, is an inflammatory disorder predominantly affecting the central face. Persons most often affected are Caucasians of northern European background, but rosacea also occurs in patients with dark skin. Rosacea is seen almost exclusively in adults, only rarely affecting patients <30 years old. Rosacea is more common in women, but those most severely affected are men. It is characterized by the presence of erythema, telangiectasias, and superficial pustules (Fig. 57-8) but is not associated with the presence of comedones. Rosacea rarely involves the chest or back.

There is a relationship between the tendency for facial flushing and the subsequent development of acne rosacea. Often, individuals with rosacea initially demonstrate a pronounced flushing reaction. This may be in response to heat, emotional stimuli, alcohol, hot drinks, or spicy foods. As the disease progresses, the flush persists longer and longer and may eventually become permanent. Papules, pustules, and telangiectasias can become superimposed on the persistent flush. Rosacea of very long standing may lead to connective tissue overgrowth, particularly of the nose (rhinophyma). Rosacea may also be complicated by various inflammatory disorders of the eye, including keratitis, blepharitis, iritis, and recurrent chalazion. These ocular problems are potentially sight-threatening and warrant ophthalmologic evaluation.

SKIN DISEASES AND SMALLPOX VACCINATION

Although smallpox vaccinations were discontinued several decades ago for the general population, they are still required for certain military personnel and first responders. In the absence of a bioterrorism attack and a real or potential exposure to smallpox, such vaccination is contraindicated in persons with a history of skin diseases, such as AD, eczema, and psoriasis, who have a higher incidence of adverse events associated with smallpox vaccination. In the case of such exposure, the risk of smallpox infection outweighs that of adverse events from the vaccine (Chap. S3).

FURTHER READING

INTRODUCTION

It is a generally accepted concept in medicine that the skin can develop signs of internal disease. Therefore, in textbooks of medicine, one finds a chapter describing in detail the major systemic disorders that can be identified by cutaneous signs. The underlying assumption of such a chapter is that the clinician has been able to identify the specific disorder in the patient and needs only to read about it in the textbook. In reality, concise differential diagnoses and the identification of these disorders are actually difficult for the nondermatologist because he or she is not well-versed in the recognition of cutaneous lesions or their spectrum of presentations. Therefore, this chapter covers this particular topic of cutaneous medicine not by simply focusing on individual diseases, but by describing the various presenting clinical signs and symptoms that point to specific disorders. Concise differential diagnoses will be generated in which the significant diseases will be distinguished from the more common cutaneous disorders that have minimal or no significance with regard to associated internal disease. The latter disorders are reviewed in table form and always need to be excluded when considering the former. For a detailed description of individual diseases, the reader should consult a dermatologic text.

PAPULOSQUAMOUS SKIN LESIONS

(Table 58-1) When an eruption is characterized by elevated lesions, either papules (<1 cm) or plaques (>1 cm), in association with scale, it is referred to as papulosquamous. The most common papulosquamous diseases—tinea, psoriasis, pityriasis rosea, and lichen planus—are primary cutaneous disorders (Chap. 57). When psoriatic lesions are accompanied by arthritis, the possibility of psoriatic arthritis or reactive arthritis should be considered. A history of oral ulcers, conjunctivitis, uveitis, and/or urethritis points to the latter diagnosis. Lithium, beta blockers, anti-PD-1/PD-L1 antibodies, HIV or streptococcal infections, and a rapid taper of systemic glucocorticoids are known to exacerbate psoriasis; despite being used to treat psoriasis, tumor necrosis factor (TNF) inhibitors can also induce psoriatic lesions. Comorbidities in patients with psoriasis include cardiovascular disease and metabolic syndrome.

Whenever the clinical diagnosis of pityriasis rosea or lichen planus is made, it is important to review the patient’s medications because the eruption may resolve by simply discontinuing the offending agent. Pityriasis rosea–like drug eruptions are seen most commonly with beta blockers, angiotensin-converting enzyme (ACE) inhibitors, and metronidazole, whereas the drugs that can produce a lichenoid eruption include thiazides, antimalarials, quinidine, beta blockers, TNF inhibitors, anti-PD-1/PD-L1 antibodies, and ACE inhibitors. In some populations (e.g., Europeans), there is a higher prevalence of hepatitis C viral infection in patients with oral lichen planus. Lichen planus–like lesions are also observed in chronic graft-versus-host disease.

In its early stages, the mycosis fungoides (MF) form of cutaneous T-cell lymphoma (CTCL) may be confused with eczema or psoriasis, but it often eventually fails to respond to appropriate therapy for those inflammatory diseases. MF can develop within lesions of large-plaque parapsoriasis and is suggested by an increase in the thickness of the lesions. The diagnosis of MF is established by skin biopsy in which collections of atypical T lymphocytes are found in the epidermis and dermis. As the disease progresses, cutaneous tumors and lymph node involvement may appear.

In secondary syphilis, there are scattered pink to red-brown papules with thin scale. The eruption often involves the palms and soles and can resemble pityriasis rosea. Associated findings are helpful in making the diagnosis and include nonscarring alopecia, annular plaques on the face, mucous patches, condyloma lata (broad-based and moist), and lymphadenopathy, as well as malaise, fever, headache, and myalgias. The interval between the primary chancre and the secondary stage is usually 4–8 weeks, and spontaneous resolution without appropriate therapy occurs.

ERYTHRODERMA

(Table 58-2) Erythroderma is the term used when the majority of the skin surface is erythematous (red in color). There may be associated scale, erosions, or pustules as well as shedding of the hair and nails. Potential systemic manifestations include fever, chills, hypothermia, reactive lymphadenopathy, peripheral edema, hypoalbuminemia, and high-output cardiac failure. The major etiologies of erythroderma are (1) cutaneous diseases such as psoriasis and dermatitis (Table 58-3); (2) drugs; (3) systemic diseases, most commonly CTCL; and (4) idiopathic. In the first three groups, the location and description of the initial lesions, prior to the development of the erythroderma, aid in the diagnosis. For example, a history of red scaly plaques on the elbows and knees would point to psoriasis. It is also important to examine the skin carefully for a migration of the erythema and associated secondary changes such as pustules or erosions. Migratory waves of erythema studded with superficial pustules are seen in pustular psoriasis.

Drug-induced erythroderma may begin as an exanthematous (morbilliform) eruption (Chap. 60) or may arise as diffuse erythema. A number of drugs can produce an erythroderma, including penicillins, sulfonamides, aromatic anticonvulsants (e.g., carbamazepine, phenytoin), and allopurinol. Fever and peripheral eosinophilia often accompany the eruption, and there may also be facial swelling, hepatitis, myocarditis, thyroiditis, and allergic interstitial nephritis; this constellation is frequently referred to as drug reaction with eosinophilia and systemic symptoms (DRESS) or drug-induced hypersensitivity syndrome (DIHS). In addition, these reactions, especially to aromatic anticonvulsants, can lead to a pseudolymphoma syndrome with adenopathy and circulating atypical lymphocytes, while reactions to allopurinol may be accompanied by gastrointestinal bleeding.

The most common malignancy that is associated with erythroderma is CTCL; in some series, up to 25% of the cases of erythroderma were due to CTCL. The patient may progress from isolated plaques and tumors, but more commonly, the erythroderma is present throughout the course of the disease (Sézary syndrome). In Sézary syndrome, there are circulating clonal atypical T lymphocytes, pruritus, and lymphadenopathy. In cases of erythroderma where there is no apparent cause (idiopathic), longitudinal evaluation is mandatory to monitor for the possible development of CTCL.

ALOPECIA

(Table 58-4) The two major forms of alopecia are scarring and nonscarring. Scarring alopecia is associated with fibrosis, inflammation, and loss of hair follicles. A smooth scalp with a decreased number of follicular openings is usually observed clinically, but in some patients, the changes are seen only in biopsy specimens from affected areas. In nonscarring alopecia, the hair shafts are absent or miniaturized, but the hair follicles are preserved, explaining the reversible nature of nonscarring alopecia.

The most common causes of nonscarring alopecia include androgenetic alopecia, telogen effluvium, alopecia areata, tinea capitis, and the early phase of traumatic alopecia (Table 58-5). In women with androgenetic alopecia, an elevation in circulating levels of androgens may be seen as a result of ovarian or adrenal gland dysfunction or neoplasm. When there are signs of virilization, such as a deepened voice and/or enlarged clitoris, the possibility of an ovarian or adrenal gland tumor should be considered.

Exposure to various drugs can also cause diffuse hair loss, usually by inducing a telogen effluvium. An exception is the anagen effluvium observed with chemotherapeutic agents such as daunorubicin. Alopecia is a side effect of the following drugs: warfarin, heparin, propylthiouracil, carbimazole, isotretinoin, acitretin, lithium, beta blockers, interferons, colchicine, and amphetamines. Fortunately, spontaneous regrowth usually follows discontinuation of the offending agent.

Less commonly, nonscarring alopecia is associated with lupus erythematosus and secondary syphilis. In systemic lupus, there are two forms of alopecia—one is scarring secondary to discoid lesions (see below), and the other is nonscarring. The latter form coincides with flares of systemic disease and may involve the entire scalp or just the frontal scalp, with the appearance of multiple short hairs (“lupus hairs”) as a sign of initial regrowth. Scattered, poorly circumscribed patches of alopecia with a “moth-eaten” appearance are a manifestation of the secondary stage of syphilis. Diffuse thinning of the hair is also associated with hypothyroidism and hyperthyroidism (Table 58-4).

Scarring alopecia is more frequently the result of a primary cutaneous disorder such as lichen planus, chronic cutaneous (discoid) lupus, central centrifugal cicatricial alopecia, folliculitis decalvans, or linear scleroderma (morphea) than it is a sign of systemic disease. Although the scarring lesions of discoid lupus can be seen in patients with systemic lupus, in the majority of patients, the disease process is limited to the skin. Less common causes of scarring alopecia include sarcoidosis (see “Papulonodular Skin Lesions,” below), chemotherapeutic agents, and cutaneous metastases.

In the early phases of discoid lupus, lichen planus, and folliculitis decalvans, there are circumscribed areas of alopecia. Fibrosis and subsequent loss of hair follicles are observed primarily in the center of these alopecic patches, whereas the inflammatory process is most prominent at the periphery. The areas of active inflammation in discoid lupus are erythematous with scale, whereas the areas of previous inflammation are often hypopigmented with a rim of hyperpigmentation. In lichen planus, perifollicular macules at the periphery are usually violet-colored. A complete examination of the skin and oral mucosa combined with a biopsy and direct immunofluorescence microscopy of inflamed skin will aid in distinguishing these two entities. The peripheral active lesions in folliculitis decalvans are follicular pustules; these patients can develop a reactive arthritis.

FIGURATE SKIN LESIONS

(Table 58-6) In figurate eruptions, the lesions form rings and arcs that are usually erythematous but can be skin-colored to brown. Most commonly, they are due to primary cutaneous diseases such as tinea, urticaria, granuloma annulare, and erythema annulare centrifugum (Chaps. 57 and 59). An underlying systemic illness is found in a second, less common group of migratory annular erythemas. It includes erythema migrans, erythema gyratum repens, erythema marginatum, and necrolytic migratory erythema.

In erythema gyratum repens, one sees numerous mobile concentric arcs and wavefronts that resemble the grain in wood. A search for an underlying malignancy is mandatory in a patient with this eruption. Erythema migrans is the cutaneous manifestation of Lyme disease, which is caused by the spirochete Borrelia burgdorferi. In the initial stage (3–30 days after tick bite), a single annular lesion is usually seen, which can expand to ≥10 cm in diameter. Within several days, up to half of the patients develop multiple smaller erythematous lesions at sites distant from the bite. Associated symptoms include fever, headache, photophobia, myalgias, arthralgias, and malar rash. Erythema marginatum is seen in patients with rheumatic fever, primarily on the trunk. Lesions are pink-red in color, flat to minimally elevated, and transient.

There are additional cutaneous diseases that present as annular eruptions but lack an obvious migratory component. Examples include CTCL, subacute cutaneous lupus, secondary syphilis, and sarcoidosis (see “Papulonodular Skin Lesions,” below).

ACNE

(Table 58-7) In addition to acne vulgaris and acne rosacea, the two major forms of acne (Chap. 57), there are drugs and systemic diseases that can lead to acneiform eruptions.

Patients with the carcinoid syndrome have episodes of flushing of the head, neck, and sometimes the trunk. Resultant skin changes of the face, in particular telangiectasias, may mimic the clinical appearance of erythematotelangiectatic acne rosacea.

PUSTULAR LESIONS

Acneiform eruptions (see “Acne,” above) and folliculitis represent the most common pustular dermatoses. An important consideration in the evaluation of follicular pustules is a determination of the associated pathogen, for example, normal flora (culture-negative), Staphylococcus aureus, Pseudomonas aeruginosa (“hot tub” folliculitis), Malassezia, dermatophytes (Majocchi’s granuloma), and Demodex spp. Noninfectious forms of folliculitis include HIV- or immunosuppression-associated eosinophilic folliculitis and folliculitis secondary to drugs such as glucocorticoids, lithium, and epidermal growth factor receptor (EGFR) or MEK inhibitors. Administration of high-dose systemic glucocorticoids can result in a widespread eruption of follicular pustules on the trunk, characterized by lesions in the same stage of development. With regard to underlying systemic diseases, nonfollicular-based pustules are a characteristic component of pustular psoriasis (sterile) and can be seen in septic emboli of bacterial or fungal origin (see “Purpura,” below). In patients with acute generalized exanthematous pustulosis (AGEP) due primarily to medications (e.g., cephalosporins), there are large areas of erythema studded with multiple sterile pustules in addition to neutrophilia.

TELANGIECTASIAS

(Table 58-8) To distinguish the various types of telangiectasias, it is important to examine the shape and configuration of the dilated blood vessels. Linear telangiectasias are seen on the face of patients with actinically damaged skin and acne rosacea, and they are found on the legs of patients with venous hypertension and first appear on the legs in generalized essential telangiectasia. Patients with an unusual form of mastocytosis (telangiectasia macularis eruptiva perstans) and the carcinoid syndrome (see “Acne,” above) also have linear telangiectasias. Lastly, linear telangiectasias are found in areas of cutaneous inflammation. For example, longstanding lesions of discoid lupus frequently have telangiectasias within them.

Poikiloderma is a term used to describe a patch of skin with: (1) reticulated hypo- and hyperpigmentation, (2) wrinkling secondary to epidermal atrophy, and (3) telangiectasias. Poikiloderma does not imply a single disease entity—although it is becoming less common, it is seen in skin damaged by ionizing radiation as well as in patients with autoimmune connective tissue diseases, primarily dermatomyositis (DM), and rare genodermatoses (e.g., Kindler syndrome).

In systemic sclerosis (scleroderma), the dilated blood vessels have a unique configuration and are known as mat telangiectasias. The lesions are broad macules that usually measure 2–7 mm in diameter but occasionally are larger. Mats have a polygonal or oval shape, and their erythematous color may appear uniform, but, upon closer inspection, the erythema is the result of delicate telangiectasias. The most common locations for mat telangiectasias are the face, oral mucosa, and hands—peripheral sites that are prone to intermittent ischemia. The limited form of systemic sclerosis, also referred to as the CREST (calcinosis cutis, Raynaud’s phenomenon, esophageal dysmotility, sclerodactyly, and telangiectasia) variant (Chap. 360), is associated with a chronic course and anticentromere antibodies. Mat telangiectasias are an important clue to the diagnosis of this variant as well as the diffuse form of systemic sclerosis because they may be the only cutaneous finding.

Nailfold telangiectasias are pathognomonic signs of the three major autoimmune connective tissue diseases: lupus erythematosus, systemic sclerosis, and DM. They are easily visualized by the naked eye and occur in at least two-thirds of these patients. In both DM and lupus, there is associated nailfold erythema, and in DM, the erythema is often accompanied by “ragged” cuticles and fingertip tenderness. Under 10× magnification or by dermoscopy, the blood vessels in the nailfolds of lupus patients are tortuous and resemble “glomeruli,” whereas in systemic sclerosis and DM, there is a loss of capillary loops and those that remain are markedly dilated.

In hereditary hemorrhagic telangiectasia (Osler-Rendu-Weber disease), the lesions usually appear during adolescence (mucosal) and adulthood (cutaneous) and are most commonly seen on the mucous membranes (nasal, orolabial), face, and distal extremities, including under the nails. They represent arteriovenous (AV) malformations of the dermal microvasculature, are dark red in color, and are usually slightly elevated. When the skin is stretched over an individual lesion, an eccentric punctum with radiating legs is seen. Although the degree of systemic involvement varies in this autosomal dominant disease (due primarily to mutations in either the endoglin or activin receptor–like kinase gene), the major symptoms are recurrent epistaxis and gastrointestinal bleeding. The fact that these mucosal telangiectasias are actually AV communications helps to explain their tendency to bleed.

HYPOPIGMENTATION

(Table 58-9) Disorders of hypopigmentation are often classified as either diffuse or localized. The classic example of diffuse hypopigmentation is oculocutaneous albinism (OCA). The most common forms are due to mutations in the tyrosinase gene (type I) or the P gene (type II); patients with type IA OCA have a total lack of enzyme activity. At birth, different forms of OCA can appear similar—white hair, gray-blue eyes, and pink-white skin. However, the patients with no tyrosinase activity maintain this phenotype, whereas those with decreased activity will acquire some pigmentation of the eyes, hair, and skin as they age. The degree of pigment formation is also a function of racial background, and the pigmentary dilution is more readily apparent when patients are compared to their first-degree relatives. The ocular findings in OCA correlate with the degree of hypopigmentation and include decreased visual acuity, nystagmus, photophobia, strabismus, and a lack of normal binocular vision.

The differential diagnosis of localized hypomelanosis includes the following primary cutaneous disorders: postinflammatory hypopigmentation, idiopathic guttate hypomelanosis, pityriasis (tinea) versicolor, vitiligo, chemical- or drug-induced leukoderma, nevus depigmentosus (see below), progressive macular hypomelanosis, and piebaldism (Table 58-10). In this group of diseases, the areas of involvement are macules or patches with a decrease or absence of pigmentation. Patients with vitiligo also have an increased incidence of several autoimmune disorders, including Hashimoto’s thyroiditis, Graves’ disease, pernicious anemia, Addison’s disease, uveitis, alopecia areata, chronic mucocutaneous candidiasis, and the autoimmune polyendocrine syndromes (types I and II). Diseases of the thyroid gland are the most frequently associated disorders, occurring in up to 30% of patients with vitiligo. Circulating autoantibodies are often found, and the most common ones are antithyroglobulin, antimicrosomal, and antithyroid-stimulating hormone receptor antibodies.

There are four systemic diseases that should be considered in a patient with skin findings suggestive of vitiligo—systemic sclerosis, melanoma-associated leukoderma, onchocerciasis, and Vogt-Koyanagi-Harada syndrome. The vitiligo-like leukoderma seen in patients with systemic sclerosis has a clinical resemblance to idiopathic vitiligo that has begun to repigment as a result of treatment; that is, perifollicular macules of normal pigmentation are seen within areas of depigmentation. The basis of this leukoderma is unknown; there is no evidence of inflammation in areas of involvement, but it can resolve if the underlying connective tissue disease becomes inactive. In contrast to idiopathic vitiligo, melanoma-associated vitiligo-like leukoderma often begins on the trunk, and its appearance, if spontaneous, should prompt a search for metastatic disease. It is also seen in patients undergoing immunotherapy for melanoma, including immune checkpoint-blocking antibodies, with cytotoxic T lymphocytes presumably recognizing cell surface antigens common to melanoma cells and melanocytes, and is associated with a greater likelihood of a clinical response. A history of aseptic meningitis, nontraumatic uveitis, tinnitus, hearing loss, and/or dysacousia points to the diagnosis of the Vogt-Koyanagi-Harada syndrome. In these patients, the face and scalp are the most common locations of pigment loss.

There are two systemic disorders (neurocristopathies) that may have the cutaneous findings of piebaldism (Table 58-9). They are Shah-Waardenburg syndrome and Waardenburg syndrome. A possible explanation for both disorders is an abnormal embryonic migration or survival of two neural crest–derived elements, one of them being melanocytes and the other myenteric ganglion cells (leading to Hirschsprung disease in Shah-Waardenburg syndrome) or auditory nerve cells (Waardenburg syndrome). The latter syndrome is characterized by congenital sensorineural hearing loss, dystopia canthorum (lateral displacement of the inner canthi but normal interpupillary distance), heterochromic irises, and a broad nasal root, in addition to the piebaldism. The facial dysmorphism can be explained by the neural crest origin of the connective tissues of the head and neck. Patients with Waardenburg syndrome have been shown to have mutations in four genes, including PAX-3 and MITF, all of which encode transcription factors, whereas patients with Hirschsprung disease plus white spotting have mutations in one of three genes—endothelin 3, endothelin B receptor, and SOX-10.

In tuberous sclerosis, the earliest cutaneous sign is macular hypomelanosis, referred to as an ash leaf spot. These lesions are often present at birth and are usually multiple; however, detection may require Wood’s lamp examination, especially in lightly pigmented individuals. The pigment within them is reduced, but not absent. The average size is 1–3 cm, and the common shapes are polygonal and lance-ovate. Examination of the patient for additional cutaneous signs such as multiple angiofibromas of the face (adenoma sebaceum), ungual and intraoral fibromas, fibrous cephalic plaques, and connective tissue nevi (shagreen patches) is recommended. It is important to remember that an ash leaf spot on the scalp will result in a circumscribed patch of lightly pigmented hair. Internal manifestations include seizures, intellectual disability, central nervous system (CNS) and retinal hamartomas, pulmonary lymphangioleiomyomatosis (women), renal angiomyolipomas, and cardiac rhabdomyomas. The latter can be detected in up to 60% of children (<18 years) with tuberous sclerosis by echocardiography.

Nevus depigmentosus is a stable, well-circumscribed hypomelanosis that is present at birth. There is usually a single oval or rectangular lesion, but when there are multiple lesions, the possibility of tuberous sclerosis needs to be considered. In linear nevoid hypopigmentation, a term that is replacing hypomelanosis of Ito and segmental or systematized nevus depigmentosus, streaks and swirls of hypopigmentation are observed. Up to one-third of patients in a tertiary care setting had associated abnormalities involving the musculoskeletal system (asymmetry), the CNS (seizures and intellectual disability), and the eyes (strabismus and hypertelorism). Chromosomal mosaicism has been detected in these patients, lending support to the hypothesis that the cutaneous pattern is the result of the migration of two clones of primordial melanocytes, each with a different pigment potential.

Localized areas of decreased pigmentation are commonly seen as a result of cutaneous inflammation (Table 58-10) and have been observed in the skin overlying active lesions of sarcoidosis (see “Papulonodular Skin Lesions,” below) as well as in CTCL. Cutaneous infections also present as disorders of hypopigmentation, and in tuberculoid leprosy, there are a few asymmetric patches of hypomelanosis that have associated anesthesia, anhidrosis, and alopecia. Biopsy specimens of the palpable border show dermal granulomas that contain rare, if any, Mycobacterium leprae organisms.

HYPERPIGMENTATION

(Table 58-11) Disorders of hyperpigmentation are also divided into two major groups—localized and diffuse. The localized forms are due to an epidermal alteration, a proliferation of melanocytes, or an increase in pigment production. Both acanthosis nigricans and seborrheic keratoses belong to the first group. Acanthosis nigricans can be a reflection of an internal malignancy, most commonly of the gastrointestinal tract, and it appears as velvety hyperpigmentation, primarily in flexural areas. However, in the majority of patients, acanthosis nigricans is associated with obesity and insulin resistance, although it may be a reflection of an endocrinopathy such as acromegaly, Cushing’s syndrome, polycystic ovary syndrome, or insulin-resistant diabetes mellitus (type A, type B, and lipodystrophic forms). Seborrheic keratoses are common lesions, but in one rare clinical setting, they are a sign of systemic disease, and that setting is the sudden appearance of multiple lesions, often with an inflammatory base and in association with acrochordons (skin tags) and acanthosis nigricans. This is termed the sign of Leser-Trélat and alerts the clinician to search for an internal malignancy.

A proliferation of melanocytes results in the following pigmented lesions: lentigo, melanocytic nevus, and melanoma (Chap. 76). In an adult, the majority of lentigines are related to sun exposure, which explains their distribution. However, in the Peutz-Jeghers and LEOPARD (lentigines; ECG abnormalities, primarily conduction defects; ocular hypertelorism; pulmonary stenosis and subaortic valvular stenosis; abnormal genitalia [cryptorchidism, hypospadias]; retardation of growth; and deafness [sensorineural]) syndromes, lentigines do serve as a clue to systemic disease. In LEOPARD/Noonan with multiple lentigines syndrome, hundreds of lentigines develop during childhood and are scattered over the entire surface of the body. The lentigines in patients with Peutz-Jeghers syndrome are located primarily around the nose and mouth, on the hands and feet, and within the oral cavity. While the pigmented macules on the face may fade with age, the oral lesions persist. However, similar intraoral lesions are also seen in Addison’s disease, in Laugier-Hunziker syndrome (no internal manifestations), and as a normal finding in darkly pigmented individuals. Patients with this autosomal dominant syndrome (due to mutations in a novel serine threonine kinase gene) have multiple benign polyps of the gastrointestinal tract, testicular or ovarian tumors, and an increased risk of developing gastrointestinal (primarily colon) and pancreatic cancers.

In the Carney complex, numerous lentigines are also seen, but they are in association with cardiac myxomas. This autosomal dominant disorder is also known as the LAMB (lentigines, atrial myxomas, mucocutaneous myxomas, and blue nevi) syndrome or NAME (nevi, atrial myxoma, myxoid neurofibroma, and ephelides [freckles]) syndrome. These patients can also have evidence of endocrine overactivity in the form of Cushing’s syndrome (pigmented nodular adrenocortical disease) and acromegaly.

The third type of localized hyperpigmentation is due to a local increase in pigment production, and it includes ephelides and café au lait macules (CALMs). While a single CALM can be seen in up to 10% of the normal population, the presence of multiple or large-sized CALMs raises the possibility of an associated genodermatosis, for example, neurofibromatosis (NF) or McCune-Albright syndrome. CALMs are flat, uniformly brown in color (usually two shades darker than uninvolved skin), and can vary in size from 0.5 to 12+ cm. More than 90% of adult patients with type I NF will have six or more CALMs measuring ≥1.5 cm in diameter. Additional findings are discussed in the section on neurofibromas (see “Papulonodular Skin Lesions,” below). In comparison with NF, the CALMs in patients with McCune-Albright syndrome (polyostotic fibrous dysplasia with precocious puberty in females due to mosaicism for an activating mutation in a G protein [G_sα] gene) are usually larger, are more irregular in outline, and tend to respect the midline.

In incontinentia pigmenti, dyskeratosis congenita, and bleomycin pigmentation, the areas of localized hyperpigmentation form a pattern—swirls and streaks in the first, reticulated in the second, and flagellate in the third. In dyskeratosis congenita, atrophic reticulated hyperpigmentation is seen on the neck, trunk, and thighs and is accompanied by nail dystrophy, pancytopenia, and leukoplakia of the oral and anal mucosae. The latter often develops into squamous cell carcinoma. In addition to the flagellate pigmentation (linear streaks) on the trunk, patients receiving bleomycin often have hyperpigmentation overlying the elbows, knees, and small joints of the hand.

Localized hyperpigmentation is seen as a side effect of several other systemic medications, including those that produce fixed drug reactions (nonsteroidal anti-inflammatory drugs [NSAIDs], sulfonamides, barbiturates, and tetracyclines) and those that can complex with melanin or iron (antimalarials and minocycline). Fixed drug eruptions recur in the exact same location as circular areas of erythema that can become bullous and then resolve as brown macules. The eruption usually appears within hours of readministration of the offending agent, and common locations include the genitalia, distal extremities, and perioral region. Chloroquine and hydroxychloroquine produce gray-brown to blue-black discoloration of the shins, hard palate, and face, while blue macules (often misdiagnosed as bruises) can be seen on the lower extremities and in sites of inflammation with prolonged minocycline administration. Estrogen in oral contraceptives can induce melasma—symmetric brown patches on the face, especially the cheeks, upper lip, and forehead. Similar changes are seen in pregnancy and in patients receiving phenytoin.

In the diffuse forms of hyperpigmentation, the darkening of the skin may be of equal intensity over the entire body or may be accentuated in sun-exposed areas. The causes of diffuse hyperpigmentation can be divided into four major groups—endocrine, metabolic, autoimmune, and drugs. The endocrinopathies that frequently have associated hyperpigmentation include Addison’s disease, Nelson’s syndrome, and ectopic adrenocorticotropic hormone (ACTH) syndrome. In these diseases, the increased pigmentation is diffuse but is accentuated in sun-exposed areas, as well as in the palmar creases, sites of friction, and scars. An overproduction of the pituitary hormones α-MSH (melanocyte-stimulating hormone) and ACTH can lead to an increase in melanocyte activity. These peptides are products of the proopiomelanocortin gene and exhibit homology, for example, α-MSH and ACTH share 13 amino acids. A minority of patients with Cushing’s disease or hyperthyroidism have generalized hyperpigmentation.

The metabolic causes of hyperpigmentation include porphyria cutanea tarda (PCT), hemochromatosis, vitamin B₁₂ deficiency, folic acid deficiency, pellagra, and malabsorption, including Whipple’s disease. In patients with PCT (see “Vesicles/Bullae,” below), the skin darkening is seen in sun-exposed areas and is a reflection of the photoreactive properties of porphyrins. The increased level of iron in the skin of patients with type 1 hemochromatosis stimulates melanin pigment production and leads to the classic bronze color. Patients with pellagra have a brown discoloration of the skin, especially in sun-exposed areas, as a result of nicotinic acid (niacin) deficiency. In the areas of increased pigmentation, there is a thin, varnish-like scale. These changes are also seen in patients who are vitamin B₆ deficient, have functioning carcinoid tumors (increased consumption of niacin), or take isoniazid. Approximately 50% of the patients with Whipple’s disease have an associated generalized hyperpigmentation in association with diarrhea, weight loss, arthritis, and lymphadenopathy. A diffuse, slate-blue to gray-brown color is seen in patients with melanosis secondary to metastatic melanoma. The color reflects widespread deposition of melanin within the dermis as a result of the high concentration of circulating melanin precursors.

Of the autoimmune diseases associated with diffuse hyperpigmentation, primary biliary cholangitis and systemic sclerosis are the most common, and occasionally, both disorders are seen in the same patient. The skin is dark brown in color, especially in sun-exposed areas. In primary biliary cholangitis, the hyperpigmentation is accompanied by pruritus, jaundice, and xanthomas, whereas in systemic sclerosis, it is accompanied by sclerosis of the extremities, face, and, less commonly, the trunk. Additional clues to the diagnosis of systemic sclerosis are mat and cuticular telangiectasias, calcinosis cutis, Raynaud’s phenomenon, and distal ulcerations (see “Telangiectasias,” above). The differential diagnosis of cutaneous sclerosis with hyperpigmentation includes POEMS (polyneuropathy; organomegaly [liver, spleen, lymph nodes]; endocrinopathies [impotence, gynecomastia]; M-protein; and skin changes) syndrome. The skin changes include hyperpigmentation, induration, hypertrichosis, angiomas, clubbing, and facial lipoatrophy.

Diffuse hyperpigmentation that is due to drugs or metals can result from one of several mechanisms—induction of melanin pigment formation, complexing of the drug or its metabolites to melanin, and deposits of the drug in the dermis. Busulfan, cyclophosphamide, 5-fluorouracil, and inorganic arsenic induce pigment production. Complexes containing melanin or iron plus the drug or its metabolites are seen in patients receiving minocycline, and a diffuse, brown-gray, muddy appearance within sun-exposed areas may develop, in addition to pigmentation of the mucous membranes, teeth, nails, bones, and thyroid. Administration of amiodarone can result in both a phototoxic eruption (exaggerated sunburn) and/or a slate-gray to violaceous discoloration of sun-exposed skin. Biopsy specimens of the latter show yellow-brown granules in dermal macrophages, which represent intralysosomal accumulations of lipids, amiodarone, and its metabolites. Actual deposits of a particular drug or metal in the skin are seen with silver (argyria), where the skin appears blue-gray in color; gold (chrysiasis), where the skin has a brown to blue-gray color; and clofazimine, where the skin appears reddish brown. The associated pigmentation is accentuated in sun-exposed areas, and discoloration of the eye is seen with gold (sclerae) and clofazimine (conjunctivae).

VESICLES/BULLAE

(Table 58-12) Depending on their size, cutaneous blisters are referred to as vesicles (<1 cm) or bullae (>1 cm). The primary autoimmune blistering disorders include pemphigus vulgaris, pemphigus foliaceus, paraneoplastic pemphigus, bullous pemphigoid, gestational pemphigoid, cicatricial pemphigoid, epidermolysis bullosa acquisita, linear IgA bullous dermatosis (LABD), and dermatitis herpetiformis (Chap. 59).

Vesicles and bullae are also seen in contact dermatitis, both allergic and irritant forms (Chap. 57). When there is a linear arrangement of vesicular lesions, an exogenous cause or herpes zoster should be suspected. Bullous disease secondary to the ingestion of drugs can take one of several forms, including phototoxic eruptions, isolated bullae, Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN) (Chap. 60). Clinically, phototoxic eruptions resemble an exaggerated sunburn with diffuse erythema and bullae in sun-exposed areas. The most commonly associated drugs are doxycycline, quinolones, voriconazole, thiazides, NSAIDs, vemurafenib, and psoralens. The development of a phototoxic eruption is dependent on the doses of both the drug and ultraviolet (UV)-A irradiation.

Toxic epidermal necrolysis is characterized by bullae that arise on widespread areas of tender erythema and then slough. This results in large areas of denuded skin. The associated morbidity, such as sepsis, and mortality rates are relatively high and are a function of the extent of epidermal necrosis. In addition, these patients may also have involvement of the mucous membranes and respiratory and intestinal tracts. Drugs are the primary cause of TEN, and the most common offenders are aromatic anticonvulsants (phenytoin, barbiturates, carbamazepine), sulfonamides, aminopenicillins, allopurinol, and NSAIDs. Generalized bullous fixed drug eruption, severe acute graft-versus-host disease (grade 4), vancomycin-induced LABD, and flares of cutaneous lupus can also resemble TEN.

In erythema multiforme (EM), the primary lesions are pink-red macules and edematous papules, the centers of which may become vesicular. In contrast to a morbilliform exanthem, the clue to the diagnosis of EM, and especially SJS, is the development of a “dusky” violet color in the center of the lesions. Target lesions are also characteristic of EM and arise as a result of active centers and borders in combination with centrifugal spread. However, target lesions need not be present to make the diagnosis of EM.

EM has been subdivided into two major groups: (1) EM minor due to herpes simplex virus (HSV); and (2) EM major due to HSV, Mycoplasma pneumonia, or, occasionally, other viruses, Chlamydia, or drugs. Involvement of the mucous membranes (ocular, nasal, oral, and genital) is seen more commonly in the latter form, and in patients with Mycoplasma pneumoniae-induced rash and mucositis (MIRM), there may be minimal cutaneous involvement. Hemorrhagic crusts of the lips are characteristic of EM major and SJS as well as herpes simplex, pemphigus vulgaris, and paraneoplastic pemphigus. Fever, malaise, myalgias, sore throat, and cough may precede or accompany the eruption. The lesions of EM usually resolve over 2–4 weeks but may be recurrent, especially when due to HSV. In addition to HSV (in which lesions usually appear 7–12 days after the viral eruption), EM can also follow vaccinations, radiation therapy, and exposure to environmental toxins, including the oleoresin in poison ivy.

Induction of SJS is most often due to drugs, especially sulfonamides, aromatic anticonvulsants, lamotrigine, aminopenicillins, and nonnucleoside reverse transcriptase inhibitors (e.g., nevirapine). Widespread dusky macules and significant mucosal involvement are characteristic of SJS, and the cutaneous lesions may or may not develop epidermal detachment. If the latter occurs, by definition, it is limited to <10% of the body surface area (BSA). Greater involvement leads to the diagnosis of SJS/TEN overlap (10–30% BSA) or TEN (>30% BSA).

In addition to primary blistering disorders and hypersensitivity reactions, bacterial and viral infections can lead to vesicles and bullae. The most common infectious agents are HSV (Chap. 192), varicella-zoster virus (Chap. 193), and S. aureus (Chap. 147).

Staphylococcal scalded-skin syndrome (SSSS) and bullous impetigo are two blistering disorders associated with staphylococcal (phage group II) infection. In SSSS, the initial findings are redness and tenderness of the central face, neck, trunk, and intertriginous zones. This is followed by short-lived flaccid bullae and a slough or exfoliation of the superficial epidermis. Crusted areas then develop, characteristically around the mouth in a radial pattern. SSSS is distinguished from TEN by the following features: younger age group (primarily infants and toddlers), more superficial site of blister formation, no oral lesions, shorter course, lower morbidity and mortality rates, and an association with staphylococcal exfoliative toxin (“exfoliatin”), not drugs. A rapid diagnosis of SSSS versus TEN can be made by a frozen section of the blister roof or exfoliative cytology of the blister contents. In SSSS, the site of staphylococcal infection is usually extracutaneous (conjunctivitis, rhinorrhea, otitis media, pharyngitis, tonsillitis), and the cutaneous lesions are sterile, whereas in bullous impetigo, the skin lesions are the site of infection. Impetigo is more localized than SSSS and usually presents with honey-colored crusts. Occasionally, superficial purulent blisters also form. Cutaneous emboli from gram-negative infections may present as isolated bullae, but the base of the lesion is purpuric or necrotic, and it may develop into an ulcer (see “Purpura,” below).

Several metabolic disorders are associated with blister formation, including diabetes mellitus, renal failure, and porphyria. Local hypoxemia secondary to decreased cutaneous blood flow can also produce blisters, which explains the presence of bullae over pressure points in comatose patients (coma bullae). In diabetes mellitus, tense bullae with clear sterile viscous fluid arise on normal skin. The lesions can be as large as 6 cm in diameter and are located on the distal extremities. There are several types of porphyria, but the most common form with cutaneous findings is porphyria cutanea tarda (PCT). In sun-exposed areas (primarily the hands), the skin is very fragile, with trauma leading to erosions mixed with tense vesicles. These lesions then heal with scarring and formation of milia; the latter are firm, 1- to 2-mm white or yellow papules that represent epidermoid cysts. Associated findings can include hypertrichosis of the lateral malar region (men) or face (women) and, in sun-exposed areas, hyperpigmentation and firm sclerotic plaques. An elevated level of urinary uroporphyrins confirms the diagnosis and is due to a decrease in uroporphyrinogen decarboxylase activity. PCT can be exacerbated by alcohol, hemochromatosis and other forms of iron overload, chlorinated hydrocarbons, hepatitis C virus and HIV infections, and hepatomas.

The differential diagnosis of PCT includes (1) porphyria variegata—the skin signs of PCT plus the systemic findings of acute intermittent porphyria; it has a diagnostic plasma porphyrin fluorescence emission at 626 nm; (2) drug-induced pseudoporphyria—the clinical and histologic findings are similar to PCT, but porphyrins are normal; etiologic agents include naproxen and other NSAIDs, furosemide, tetracycline, and voriconazole; (3) bullous dermatosis of hemodialysis—the same appearance as PCT, but porphyrins are usually normal or occasionally borderline elevated; patients have chronic renal failure and are on hemodialysis; (4) PCT associated with hepatomas and hemodialysis; and (5) epidermolysis bullosa acquisita (Chap. 59).

EXANTHEMS

(Table 58-13) Exanthems are characterized by an acute generalized eruption. The most common presentation is erythematous macules and papules (morbilliform) and less often confluent blanching erythema (scarlatiniform). Morbilliform eruptions are usually due to either drugs or viral infections. For example, up to 5% of patients receiving penicillins, sulfonamides, phenytoin, or nevirapine will develop a maculopapular eruption. Accompanying signs may include pruritus, fever, eosinophilia, transaminitis, and transient lymphadenopathy (Chap. 60). Similar maculopapular eruptions are seen in the classic childhood viral exanthems, including (1) rubeola (measles)—a prodrome of coryza, cough, and conjunctivitis followed by Koplik’s spots on the buccal mucosa; the eruption begins behind the ears, at the hairline, and on the forehead and then spreads down the body, often becoming confluent; (2) rubella—the eruption begins on the forehead and face and then spreads down the body; it resolves in the same order and is associated with retroauricular and suboccipital lymphadenopathy; and (3) erythema infectiosum (fifth disease)—erythema of the cheeks is followed by a reticulated pattern on the extremities; it is secondary to a parvovirus B19 infection, and an associated arthritis is seen in adults.

Both measles and rubella can occur in unvaccinated adults, and an atypical form of measles is seen in adults immunized with either killed measles vaccine or killed vaccine followed in time by live vaccine. In contrast to classic measles, the eruption of atypical measles begins on the palms, soles, wrists, and ankles, and the lesions may become purpuric. The patient with atypical measles can have pulmonary involvement and be quite ill. Rubelliform and roseoliform eruptions are also associated with Epstein-Barr virus (5–15% of patients), echovirus, coxsackievirus, cytomegalovirus, adenovirus, SARS-CoV-2, and dengue, chikungunya, and West Nile virus infections. Detection of specific IgM antibodies or fourfold elevations in IgG antibodies often allows the proper diagnosis, but polymerase chain reaction (PCR) is gradually replacing serologic assays. Occasionally, a maculopapular drug eruption is a reflection of an underlying viral infection. For example, ~95% of the patients with infectious mononucleosis who are given ampicillin will develop a rash.

Of note, early in the course of infections with Rickettsia and meningococcus, prior to the development of petechiae and purpura, the lesions may be erythematous macules and papules. This is also the case in chickenpox prior to the development of vesicles. Maculopapular eruptions are associated with early HIV infection, early secondary syphilis, typhoid fever, and acute graft-versus-host disease. In the last, lesions frequently begin on the dorsal hands and forearms; the macular rose spots of typhoid fever involve primarily the anterior trunk.

The prototypic scarlatiniform eruption is seen in scarlet fever and is due to an erythrogenic toxin produced by bacteriophage-containing group A β-hemolytic streptococci, most commonly in the setting of pharyngitis. This eruption is characterized by diffuse erythema, which begins on the neck and upper trunk, and red follicular puncta. Additional findings include a white strawberry tongue (white coating with red papillae) followed by a red strawberry tongue (red tongue with red papillae); petechiae of the palate; a facial flush with circumoral pallor; linear petechiae in the antecubital fossae; and desquamation of the involved skin, palms, and soles 5–20 days after onset of the eruption. A similar desquamation of the palms and soles is seen in toxic shock syndrome (TSS), in Kawasaki disease, and after severe febrile illnesses. Certain strains of staphylococci also produce an erythrotoxin that leads to the same clinical findings as in streptococcal scarlet fever, except that the anti-streptolysin O or DNase B titers are not elevated.

In toxic shock syndrome, staphylococcal (phage group I) infections produce an exotoxin (TSST-1) that causes the fever and rash as well as enterotoxins. Initially, the majority of cases were reported in menstruating women who were using tampons. However, other sites of infection, including wounds and nasal packing, can lead to TSS. The diagnosis of TSS is based on clinical criteria (Chap. 147), and three of these involve mucocutaneous sites (diffuse erythema of the skin, desquamation of the palms and soles 1–2 weeks after onset of illness, and involvement of the mucous membranes). The latter is characterized as hyperemia of the vagina, oropharynx, or conjunctivae. Similar systemic findings have been described in streptococcal toxic shock syndrome (Chap. 148), and although an exanthem is seen less often than in TSS due to a staphylococcal infection, the underlying infection is often in the soft tissue (e.g., cellulitis).

The cutaneous eruption in Kawasaki disease (Chap. 363) is polymorphous, but the two most common forms are morbilliform and scarlatiniform. Additional mucocutaneous findings include bilateral conjunctival injection; erythema and edema of the hands and feet followed by desquamation; and diffuse erythema of the oropharynx, red strawberry tongue, and dry fissured lips. This clinical picture can resemble TSS and scarlet fever, but clues to the diagnosis of Kawasaki disease are cervical lymphadenopathy, cheilitis, and thrombocytosis. The most serious associated systemic finding in this disease is coronary aneurysms secondary to arteritis. Seen primarily in children, SARS-CoV-2-associated multisystem inflammatory syndrome must be distinguished from Kawasaki disease. Scarlatiniform eruptions are also seen in the early phase of SSSS (see “Vesicles/Bullae,” above), in young adults with Arcanobacterium haemolyticum infection, and as reactions to drugs.

URTICARIA

(Table 58-14) Urticaria (hives) are transient lesions that are composed of a central wheal surrounded by an erythematous halo or flare. Individual lesions are round, oval, or figurate and are often pruritic. Acute and chronic urticarias have a wide variety of allergic etiologies and reflect edema in the dermis. Urticarial lesions can also be seen in patients with mastocytosis (urticaria pigmentosa), hypo- or hyperthyroidism, Schnitzler’s syndrome, and systemic-onset juvenile idiopathic arthritis (Still’s disease). In both juvenile- and adult-onset Still’s disease, the lesions coincide with the fever spike, are transient, and are due to dermal infiltrates of neutrophils; the latter is also referred to as neutrophilic urticarial dermatosis.

The common physical urticarias include dermographism, solar urticaria, cold urticaria, and cholinergic urticaria. Patients with dermographism exhibit linear wheals following minor pressure or scratching of the skin and may be a contributing factor to pruritic dermatoses. It is a common disorder, affecting ~5% of the population. Solar urticaria characteristically occurs within minutes of sun exposure and is a skin sign of one systemic disease—erythropoietic protoporphyria. In addition to the urticaria, these patients have subtle pitted scarring of the nose and hands. Cold urticaria is precipitated by exposure to the cold, and therefore, exposed areas are usually affected. In occasional patients, the disease is associated with abnormal circulating proteins—more commonly cryoglobulins and less commonly cryofibrinogens. Additional systemic symptoms include wheezing and syncope, thus explaining the need for these patients to avoid swimming in cold water. Autosomal dominantly inherited cold urticaria is associated with dysfunction of cryopyrin. Cholinergic urticaria is precipitated by heat, exercise, or emotion and is characterized by small wheals with relatively large flares. It is occasionally associated with wheezing.

Whereas urticarias are the result of dermal edema, subcutaneous edema leads to the clinical picture of angioedema. Sites of involvement include the eyelids, lips, tongue, larynx, and gastrointestinal tract as well as the subcutaneous tissue. Angioedema occurs alone or in combination with urticaria, including urticarial vasculitis and the physical urticarias. Both acquired and hereditary (autosomal dominant) forms of angioedema occur (Chap. 354), and in the latter, urticaria is rarely, if ever, seen.

Urticarial vasculitis is an immune complex disease that may be confused with simple urticaria. In contrast to simple urticaria, individual lesions tend to last longer than 24 h and usually develop central petechiae that can be observed even after the urticarial phase has resolved. The patient may also complain of burning rather than pruritus. On biopsy, there is a leukocytoclastic vasculitis of the small dermal blood vessels. Although urticarial vasculitis may be idiopathic in origin, it can be a reflection of an underlying systemic illness such as lupus erythematosus, Sjögren’s syndrome, or hereditary complement deficiency. There is a spectrum of urticarial vasculitis that ranges from purely cutaneous to multisystem involvement. The most common systemic signs and symptoms are arthralgias and/or arthritis, nephritis, and crampy abdominal pain, with asthma and chronic obstructive lung disease seen less often. Hypocomplementemia occurs in one- to two-thirds of patients, even in the idiopathic cases. Urticarial vasculitis can also be seen in patients with hepatitis B and hepatitis C infections and serum sickness, but is usually not seen in serum sickness–like illnesses (e.g., due to cefaclor, minocycline).

PAPULONODULAR SKIN LESIONS

(Table 58-15) In the papulonodular diseases, the lesions are elevated above the surface of the skin and may coalesce to form larger plaques. The location, consistency, and color of the lesions are the keys to their diagnosis; this section is organized on the basis of color.

WHITE LESIONS

In calcinosis cutis, there are firm white to white-yellow papules with an irregular surface. When the contents are expressed, a chalky white material is seen. Dystrophic calcification is seen at sites of previous inflammation or damage to the skin. It develops in acne scars as well as on the distal extremities of patients with systemic sclerosis and in the subcutaneous tissue and intermuscular fascial planes in DM. The latter is more extensive and is more commonly seen in children. An elevated calcium phosphate product, most commonly due to secondary hyperparathyroidism in the setting of renal failure, can lead to nodules of metastatic calcinosis cutis, which tend to be subcutaneous and periarticular. These patients can also develop calcification of muscular arteries and subsequent ischemic necrosis (calciphylaxis). Osteoma cutis, in the form of small papules, most commonly occurs on the face of individuals with a history of acne vulgaris, whereas plate-like lesions occur in rare genetic syndromes.

SKIN-COLORED LESIONS

There are several types of skin-colored lesions, including epidermoid cysts, lipomas, rheumatoid nodules, neurofibromas, angiofibromas, neuromas, and adnexal tumors such as tricholemmomas. Both epidermoid cysts and lipomas are very common mobile subcutaneous nodules—the former are rubbery and drain cheeselike material (sebum and keratin) if incised. Lipomas are firm and somewhat lobulated on palpation. When extensive facial epidermoid cysts develop during childhood or there is a family history of such lesions, the patient should be examined for other signs of Gardner syndrome, including osteomas and desmoid tumors. Rheumatoid nodules are firm 0.5- to 4-cm nodules that favor the extensor aspect of joints, especially the elbows. They are seen in ~20% of patients with rheumatoid arthritis and 6% of patients with Still’s disease. Biopsies of the nodules show palisading granulomas. Similar lesions that are smaller and shorter-lived are seen in rheumatic fever.

Neurofibromas (benign Schwann cell tumors) are soft papules or nodules that exhibit the “button-hole” sign; that is, they invaginate into the skin with pressure in a manner similar to a hernia. Single lesions are seen in normal individuals, but multiple neurofibromas, usually in combination with six or more CALMs measuring >1.5 cm (see “Hyperpigmentation,” above), axillary freckling, and multiple Lisch nodules, are seen in von Recklinghausen’s disease (NF type I) (Chap. 90). In some patients, the neurofibromas are localized and unilateral due to somatic mosaicism.

Angiofibromas are firm pink-red to skin-colored papules that measure from 3 mm to 1.5 cm in diameter. When multiple lesions are located on the central cheeks (adenoma sebaceum), the patient has tuberous sclerosis or multiple endocrine neoplasia (MEN) syndrome, type 1. The former is an autosomal disorder due to mutations in two different genes, and the associated findings are discussed in the section on ash leaf spots as well as in Chap. 90.

Neuromas (benign proliferations of nerve fibers) are also firm, skin-colored papules. They are more commonly found at sites of amputations and in rudimentary polydactyly. However, when there are multiple neuromas on the eyelids, lips, distal tongue, and/or oral mucosa, the patient should be investigated for other signs of MEN syndrome, type 2b. Associated findings include marfanoid habitus, protuberant lips, intestinal ganglioneuromas, and medullary thyroid carcinoma (>75% of patients; Chap. 388).

Adnexal tumors are derived from pluripotent cells of the epidermis that can differentiate toward hair, sebaceous, or apocrine or eccrine glands, or remain undifferentiated. Basal cell carcinomas (BCCs) are examples of adnexal tumors that have little or no evidence of differentiation. Clinically, they are translucent papules with rolled borders, telangiectasias, and central erosion. BCCs commonly arise in sun-damaged skin of the head and neck as well as the upper trunk. When a patient has multiple BCCs, especially prior to age 30, the possibility of the basal cell nevus syndrome should be raised. It is inherited as an autosomal dominant trait and is associated with jaw cysts, palmar and plantar pits, frontal bossing, medulloblastomas, and calcification of the falx cerebri and diaphragma sellae. Tricholemmomas are also skin-colored adnexal tumors but differentiate toward hair follicles and can have a wartlike appearance. The presence of multiple tricholemmomas on the face and cobblestoning of the oral mucosa points to the diagnosis of Cowden disease (multiple hamartoma syndrome) due to mutations in the phosphatase and tensin homolog (PTEN) gene. Internal organ involvement (in decreasing order of frequency) includes fibrocystic disease and carcinoma of the breast, adenomas and carcinomas of the thyroid, and gastrointestinal polyposis. Keratoses of the palms, soles, and dorsal aspect of the hands are also seen. Fibrofolliculomas are skin-colored to white, smooth papules that favor the face, ears, and neck and, when multiple, are associated with Birt-Hogg-Dubé syndrome, which is associated with renal lesions including cancer (Chap. 85).

PINK LESIONS

The cutaneous lesions associated with primary systemic amyloidosis are often pink to pink-orange in color and translucent. Common locations are the face, especially the periorbital and perioral regions, and flexural areas. On biopsy, homogeneous deposits of amyloid are seen in the dermis and in the walls of blood vessels; the latter lead to an increase in vessel wall fragility. As a result, petechiae and purpura develop in clinically normal skin as well as in lesional skin following minor trauma, hence the term pinch purpura. Amyloid deposits are also seen in the striated muscle of the tongue and result in macroglossia.

Even though specific mucocutaneous lesions are present in only ~30% of the patients with primary systemic (AL) amyloidosis, the diagnosis can be made via histologic examination of abdominal subcutaneous fat, in conjunction with a serum free light chain assay. By special staining, amyloid deposits are seen around blood vessels or individual fat cells in 40–50% of patients. There are also three forms of amyloidosis that are limited to the skin and that should not be construed as cutaneous lesions of systemic amyloidosis. They are macular amyloidosis (upper back), lichen amyloidosis (usually lower extremities), and nodular amyloidosis. In macular and lichen amyloidosis, the deposits are composed of altered epidermal keratin. Early-onset macular and lichen amyloidosis have been associated with MEN syndrome, type 2a.

Patients with multicentric reticulohistiocytosis also have pink-colored papules and nodules on the face and mucous membranes as well as on the extensor surface of the hands and forearms. They have a polyarthritis that can mimic rheumatoid arthritis clinically. On histologic examination, the papules have characteristic giant cells that are not seen in biopsies of rheumatoid nodules. Pink to skin-colored papules that are firm, 2–5 mm in diameter, and often in a linear arrangement are seen in patients with papular mucinosis. This disease is also referred to as scleromyxedema. The latter name comes from the induration of the face and extremities that may accompany the papular eruption. Biopsy specimens of the papules show localized mucin deposition, and serum protein electrophoresis plus immunofixation electrophoresis demonstrates a monoclonal spike of IgG, usually with a λ light chain.

YELLOW LESIONS

Several systemic disorders are characterized by yellow-colored cutaneous papules or plaques—hyperlipidemia (xanthomas), gout (tophi), diabetes (necrobiosis lipoidica), pseudoxanthoma elasticum, and Muir-Torre syndrome (sebaceous tumors). Eruptive xanthomas are the most common form of xanthomas and are associated with hypertriglyceridemia (primarily hyperlipoproteinemia types I, IV, and V). Crops of yellow papules with erythematous halos occur primarily on the extensor surfaces of the extremities and the buttocks, and they spontaneously involute with a fall in serum triglycerides. Types II and III result in one or more of the following types of xanthoma: xanthelasma, tendon xanthomas, and plane xanthomas. Xanthelasma are found on the eyelids, whereas tendon xanthomas are frequently associated with the Achilles and extensor finger tendons; plane xanthomas are flat and favor the palmar creases and flexural folds. Tuberous xanthomas are frequently associated with hypercholesterolemia; however, they are also seen in patients with hypertriglyceridemia and are found most frequently over the large joints or hand. Biopsy specimens of xanthomas show collections of lipid-containing macrophages (foam cells).

Patients with several disorders, including biliary cirrhosis, can have a secondary form of hyperlipidemia with associated tuberous and plane xanthomas. However, patients with plasma cell dyscrasias have normolipemic plane xanthomas. This latter form of xanthoma may be ≥12 cm in diameter and is most frequently seen on the neck, upper trunk, and flexural folds. It is important to note that the most common setting for eruptive xanthomas is uncontrolled diabetes mellitus. The least specific sign for hyperlipidemia is xanthelasma, because at least 50% of the patients with this finding have normal lipid profiles.

In tophaceous gout, there are deposits of monosodium urate in the skin around the joints, particularly those of the hands and feet. Additional sites of tophi formation include the helix of the ear and the olecranon and prepatellar bursae. The lesions are firm, yellow to yellow-white in color, and occasionally discharge a chalky material. Their size varies from 1 mm to 7 cm, and the diagnosis can be established by polarized light microscopy of the aspirated contents of a tophus. Lesions of necrobiosis lipoidica are found primarily on the shins (90%), and patients can have diabetes mellitus or develop it subsequently. Characteristic findings include a central yellow color, atrophy (transparency), telangiectasias, and a red to red-brown border. Ulcerations can also develop within the plaques. Biopsy specimens show necrobiosis of collagen and granulomatous inflammation.

In pseudoxanthoma elasticum (PXE), due to mutations in the gene ABCC6, there is an abnormal deposition of calcium on the elastic fibers of the skin, eye, and blood vessels. In the skin, the flexural areas such as the neck, axillae, antecubital fossae, and inguinal area are the primary sites of involvement. Yellow papules coalesce to form reticulated plaques that have an appearance similar to that of plucked chicken skin. In severely affected skin, hanging, redundant folds develop. Biopsy specimens of involved skin show swollen and irregularly clumped elastic fibers with deposits of calcium. In the eye, the calcium deposits in Bruch’s membrane lead to angioid streaks and choroiditis; in the arteries of the heart, kidney, gastrointestinal tract, and extremities, the deposits lead to angina, hypertension, gastrointestinal bleeding, and claudication, respectively.

Adnexal tumors that have differentiated toward sebaceous glands include sebaceous adenoma, sebaceous carcinoma, and sebaceous hyperplasia. Except for sebaceous hyperplasia, which is commonly seen on the face, these tumors are fairly rare. Patients with Muir-Torre syndrome have one or more sebaceous adenoma(s), and they can also have sebaceous carcinomas and sebaceous hyperplasia as well as keratoacanthomas. The internal manifestations of Muir-Torre syndrome include multiple carcinomas of the gastrointestinal tract (primarily colon) as well as cancers of the genitourinary tract.

RED LESIONS

Cutaneous lesions that are red in color have a wide variety of etiologies; in an attempt to simplify their identification, they will be subdivided into papules, papules/plaques, and subcutaneous nodules. Common red papules include arthropod bites and cherry hemangiomas; the latter are small, bright-red, dome-shaped papules that represent a benign proliferation of capillaries. In patients with AIDS (Chap. 202), the development of multiple red hemangioma-like lesions points to bacillary angiomatosis, and biopsy specimens show clusters of bacilli that stain positively with the Warthin-Starry stain; the pathogens have been identified as Bartonella henselae and Bartonella quintana. Disseminated visceral disease is seen primarily in immunocompromised hosts but can occur in immunocompetent individuals.

Multiple angiokeratomas are seen in Fabry disease, an X-linked recessive lysosomal storage disease that is due to a deficiency of α-galactosidase A. The lesions are red to red-purple in color and can be quite small in size (1–3 mm), with the most common location being the lower trunk. Associated findings include chronic renal disease, peripheral neuropathy, and corneal opacities (cornea verticillata). While electron photomicrographs demonstrate lamellar lipid deposits in dermal fibroblasts, pericytes, and endothelial cells, nowadays, genetic analysis is more frequently performed for diagnosis. Widespread acute eruptions of erythematous papules are discussed in the section on exanthems.

There are several infectious diseases that present as erythematous papules or nodules in a lymphocutaneous or sporotrichoid pattern, that is, in a linear arrangement along the lymphatic channels. The two most common etiologies are Sporothrix schenckii (sporotrichosis) and the atypical mycobacterium Mycobacterium marinum. The organisms are introduced as a result of trauma, and a primary inoculation site is often seen in addition to the lymphatic nodules. Additional causes include Nocardia, Leishmania, and other atypical mycobacteria and dimorphic fungi; culture or PCR of lesional tissue will aid in the diagnosis.

The diseases that are characterized by erythematous plaques with scale are reviewed in the papulosquamous section, and the various forms of dermatitis are discussed in the section on erythroderma. Additional disorders in the differential diagnosis of red papules/plaques include cellulitis, polymorphous light eruption (PMLE), cutaneous lymphoid hyperplasia (lymphocytoma cutis), cutaneous lupus, lymphoma cutis, and leukemia cutis. The first three diseases represent primary cutaneous disorders, although cellulitis may be accompanied by a bacteremia. PMLE is characterized by erythematous papules and plaques in a primarily sun-exposed distribution—dorsum of the hand, extensor forearm, and upper trunk. Lesions follow exposure to UV-B and/or UV-A, and in higher latitudes, PMLE is most severe in the late spring and early summer. A process referred to as “hardening” occurs with continued UV exposure, and the eruption fades, but in temperate climates, it recurs the next spring. PMLE must be differentiated from cutaneous lupus, and this is accomplished by observation of the natural history, histologic examination, and sometimes direct immunofluorescence of the lesions. Cutaneous lymphoid hyperplasia (pseudolymphoma) is a benign polyclonal proliferation of lymphocytes within the skin that presents as infiltrated pink-red to red-purple papules and plaques; it must be distinguished from lymphoma cutis.

Several types of red plaques are seen in patients with systemic lupus, including (1) erythematous urticarial plaques across the cheeks and nose in the classic butterfly rash; (2) erythematous discoid lesions with fine or “carpet-tack” scale, telangiectasias, central hypopigmentation, peripheral hyperpigmentation, follicular plugging, and atrophy located on the scalp, face, external ears, arms, and upper trunk; and (3) psoriasiform or annular lesions of subacute cutaneous lupus with hypopigmented centers located primarily on the extensor arms and upper trunk. Additional mucocutaneous findings include (1) a violaceous flush on the face and V of the neck; (2) photosensitivity; (3) urticarial vasculitis (see “Urticaria,” above); (4) lupus panniculitis (see below); (5) diffuse alopecia; (6) alopecia secondary to discoid lesions; (7) nailfold telangiectasias and erythema; (8) EM- or TEN-like lesions that may become bullous; (9) oral or nasal ulcers; (10) livedo reticularis; and (11) distal ulcerations secondary to Raynaud’s phenomenon, vasculitis, or livedoid vasculopathy. Patients with only discoid lesions usually have the form of lupus that is limited to the skin. However, up to 10–15% of these patients eventually develop systemic lupus. Direct immunofluorescence of involved skin, in particular discoid lesions, shows deposits of IgG or IgM and C3 in a granular distribution along the dermal-epidermal junction.

In lymphoma cutis, there is a clonal proliferation of malignant lymphocytes within the skin, and the clinical appearance resembles that of cutaneous lymphoid hyperplasia—infiltrated pink-red to red-purple papules and plaques. Lymphoma cutis can occur anywhere on the surface of the skin, whereas the sites of predilection for lymphocytomas include the malar ridge, tip of the nose, and earlobes. Patients with non-Hodgkin’s lymphomas have specific cutaneous lesions more often than those with Hodgkin’s lymphoma, and, occasionally, the skin nodules precede the development of extracutaneous non-Hodgkin’s lymphoma or represent the only site of involvement (e.g., primary cutaneous B-cell lymphoma). Arcuate lesions are sometimes seen in lymphoma and lymphocytoma cutis as well as in CTCL. Adult T-cell leukemia/lymphoma that develops in association with HTLV-1 infection is characterized by cutaneous plaques, hypercalcemia, and circulating CD25+ lymphocytes. Leukemia cutis has the same appearance as lymphoma cutis, and specific lesions are seen more commonly in monocytic leukemias than in lymphocytic or granulocytic leukemias. Cutaneous chloromas (granulocytic sarcomas) may precede the appearance of circulating blasts in acute myelogenous leukemia and, as such, represent a form of aleukemic leukemia cutis.

Sweet syndrome is characterized by pink-red to red-brown edematous plaques that are frequently painful and occur primarily on the head, neck, and upper extremities. The patients also have fever, neutrophilia, and a dense dermal infiltrate of neutrophils in the lesions. In ~10% of the patients, there is an associated malignancy, most commonly acute myelogenous leukemia. Sweet syndrome has also been reported with inflammatory bowel disease, systemic lupus erythematosus, and solid tumors (primarily of the genitourinary tract) as well as drugs (e.g., granulocyte colony-stimulating factor [G-CSF], hypomethylating agents, all-trans-retinoic acid). The differential diagnosis includes neutrophilic eccrine hidradenitis; bullous forms of pyoderma gangrenosum; and, occasionally, cellulitis. Extracutaneous sites of involvement include joints, muscles, eyes, kidneys (proteinuria, occasionally glomerulonephritis), and lungs (neutrophilic infiltrates). The idiopathic form of Sweet syndrome is seen more often in women, following a respiratory tract infection.

Common causes of erythematous subcutaneous nodules include inflamed epidermoid cysts, acne cysts, and furuncles. Panniculitis, an inflammation of the fat, also presents as subcutaneous nodules and is frequently a sign of systemic disease. There are several forms of panniculitis, including erythema nodosum, erythema induratum/nodular vasculitis, lupus panniculitis, lipodermatosclerosis, α₁-antitrypsin deficiency, factitial, and fat necrosis secondary to pancreatic disease. Except for erythema nodosum, these lesions may break down and ulcerate or heal with a scar. The shin is the most common location for the nodules of erythema nodosum, whereas the calf is the most common location for lesions of erythema induratum. In erythema nodosum, the nodules are initially red but then develop a blue bruise-like color as they resolve. Patients with erythema nodosum but no underlying systemic illness can still have fever, malaise, leukocytosis, arthralgias, and/or arthritis. However, the possibility of an underlying illness should be excluded, and the most common associations are streptococcal infections, upper respiratory viral infections, sarcoidosis, and inflammatory bowel disease, in addition to drugs (oral contraceptives, sulfonamides, penicillins, bromides, iodides, BRAF inhibitors). Less common associations include bacterial gastroenteritis (Yersinia, Salmonella) and coccidioidomycosis followed by tuberculosis, histoplasmosis, brucellosis, and infections with Chlamydia pneumoniae, Chlamydia trachomatis, Mycoplasma pneumoniae, or hepatitis B virus.

Erythema induratum and nodular vasculitis have overlapping features clinically and histologically, and whether they represent two separate entities or the ends of a single disease spectrum is a point of debate; in general, the latter is usually idiopathic and the former is associated with the presence of Mycobacterium tuberculosis DNA by PCR within skin lesions. The lesions of lupus panniculitis are found primarily on the cheeks, upper arms, and buttocks (sites of abundant fat) and are seen in both the cutaneous and systemic forms of lupus. The overlying skin may be normal, erythematous, or have the changes of discoid lupus. The subcutaneous fat necrosis that is associated with pancreatic disease is presumably secondary to circulating lipases and is seen in patients with pancreatic carcinoma as well as in patients with acute and chronic pancreatitis. In this disorder, there may be an associated arthritis, fever, and inflammation of visceral fat. Histologic examination of deep incisional biopsy specimens will aid in the diagnosis of the particular type of panniculitis.

Subcutaneous erythematous nodules are also seen in cutaneous polyarteritis nodosa and as a manifestation of systemic vasculitis when there is involvement of medium-sized vessels, for example, systemic polyarteritis nodosa, eosinophilic granulomatosis with polyangiitis, or granulomatosis with polyangiitis (Chap. 363). Cutaneous polyarteritis nodosa presents with painful subcutaneous nodules and ulcers within a red-purple, netlike pattern of livedo reticularis. The latter is due to slowed blood flow through the superficial horizontal venous plexus. The majority of lesions are found on the lower extremities, and while arthralgias and myalgias may accompany cutaneous polyarteritis nodosa, there is no evidence of systemic involvement. In both the cutaneous and systemic forms of vasculitis, skin biopsy specimens of the associated nodules will show the changes characteristic of a necrotizing vasculitis and/or granulomatous inflammation.

RED-BROWN LESIONS

The cutaneous lesions in sarcoidosis (Chap. 367) are classically red to red-brown in color, and with diascopy (pressure with a glass slide), a yellow-brown residual color is observed that is secondary to the granulomatous infiltrate. The waxy papules and plaques may be found anywhere on the skin, but the face is the most common location. Usually there are no surface changes, but occasionally, the lesions will have scale. Biopsy specimens of the papules show “naked” granulomas in the dermis, that is, granulomas surrounded by a minimal number of lymphocytes. Other cutaneous findings in sarcoidosis include annular lesions with an atrophic or scaly center, papules within scars, hypopigmented papules and patches, subcutaneous plaques, alopecia, acquired ichthyosis, erythema nodosum, and lupus pernio (see below).

The differential diagnosis of sarcoidosis includes foreign-body granulomas produced by chemicals such as beryllium and zirconium, late secondary syphilis, and lupus vulgaris. Lupus vulgaris is a form of cutaneous tuberculosis that is seen in previously infected and sensitized individuals. There is often underlying active tuberculosis elsewhere, usually in the lungs or lymph nodes. Lesions occur primarily in the head and neck region and are red-brown plaques with a yellow-brown color on diascopy. Secondary scarring can develop within the central portion of the plaques. Cultures or PCR analysis of the lesions should be performed, along with an interferon γ release assay of peripheral blood, because it is rare for the acid-fast stain to show bacilli within the dermal granulomas.

A generalized distribution of red-brown macules and papules is seen in the form of mastocytosis known as urticaria pigmentosa (Chap. 354). Each lesion represents a collection of mast cells in the dermis, with hyperpigmentation of the overlying epidermis. Stimuli such as rubbing cause these mast cells to degranulate, and this leads to the formation of localized urticaria (Darier’s sign). Additional symptoms can result from mast cell degranulation and include headache, flushing, diarrhea, and pruritus. Mast cells also infiltrate various organs such as the liver, spleen, and gastrointestinal tract, and accumulations of mast cells in the bones may produce either osteosclerotic or osteolytic lesions on radiographs. In the majority of these patients, however, the internal involvement remains indolent. A subtype of chronic cutaneous small-vessel vasculitis, erythema elevatum diutinum (EED), also presents with papules that are red-brown in color. The papules coalesce into plaques on the extensor surfaces of knees, elbows, and the small joints of the hand. Flares of EED have been associated with streptococcal infections.

BLUE LESIONS

Lesions that are blue in color are the result of vascular ectasias, hyperplasias, and tumors or melanin pigment within the dermis. Venous lakes (ectasias) are compressible dark-blue lesions that are found commonly in the head and neck region. Venous malformations are also compressible blue papulonodules and plaques that can occur anywhere on the body, including the oral mucosa. When there are multiple papulonodules rather than a single congenital lesion, the patient may have the blue rubber bleb syndrome or Maffucci’s syndrome. Patients with the blue rubber bleb syndrome also have vascular anomalies of the gastrointestinal tract that may bleed, whereas patients with Maffucci’s syndrome have associated osteochondromas. Blue nevi (moles) are seen when there are collections of pigment-producing nevus cells in the dermis. These benign papular lesions are dome-shaped and occur most commonly on the dorsum of the hand or foot or in the head and neck region.

VIOLACEOUS LESIONS

Violaceous papules and plaques are seen in lupus pernio, lymphoma cutis, and cutaneous lupus. Lupus pernio is a particular type of sarcoidosis that involves the tip and alar rim of the nose as well as the earlobes, with lesions that are violaceous in color rather than red-brown. This form of sarcoidosis is associated with involvement of the upper respiratory tract. The plaques of lymphoma cutis and cutaneous lupus may be red or violaceous in color and were discussed above.

PURPLE LESIONS

Purple-colored papules and plaques are seen in vascular tumors, such as Kaposi’s sarcoma (Chap. 202) and angiosarcoma, and when there is extravasation of red blood cells into the skin in association with inflammation, as in palpable purpura (see “Purpura,” below). Patients with congenital or acquired AV fistulas and venous hypertension can develop purple papules on the lower extremities that can resemble Kaposi’s sarcoma clinically and histologically; this condition is referred to as pseudo-Kaposi’s sarcoma (acral angiodermatitis). Angiosarcoma is found most commonly on the scalp and face of elderly patients or within areas of chronic lymphedema and presents as purple papules and plaques. In the head and neck region, the tumor often extends beyond the clinically defined borders and may be accompanied by facial edema.

BROWN AND BLACK LESIONS

Brown- and black-colored papules are reviewed in “Hyperpigmentation,” above.

CUTANEOUS METASTASES

These are discussed last because they can have a wide range of colors. Most commonly, they present as either firm, skin-colored subcutaneous nodules or firm, red to red-brown papulonodules, whereas metastatic melanoma can be pink, blue, or black in color. Cutaneous metastases develop from hematogenous or lymphatic spread and are most often due to the following primary carcinomas: in men, melanoma, oropharynx, lung, and colon; and in women, breast, melanoma, and ovary. These metastatic lesions may be the initial presentation of the carcinoma, especially when the primary site is the lung.

PURPURA

(Table 58-16) Purpura are seen when there is an extravasation of red blood cells into the dermis and, as a result, the lesions do not blanch with pressure. This is in contrast to those erythematous or violet-colored lesions that are due to localized vasodilatation—they do blanch with pressure. Purpura (≥3 mm) and petechiae (≤2 mm) are divided into two major groups: palpable and nonpalpable. The most frequent causes of nonpalpable purpura and petechiae are primary cutaneous disorders such as trauma, solar (actinic) purpura, stasis purpura, and capillaritis. Less common causes are steroid purpura and livedoid vasculopathy (see “Ulcers,” below). Solar purpura are seen primarily on the extensor forearms, whereas steroid purpura secondary to potent topical glucocorticoids or endogenous or exogenous Cushing’s syndrome can be more widespread. In both cases, there is alteration of the supporting connective tissue that surrounds the dermal blood vessels. In contrast, the petechiae that result from capillaritis are found primarily on the lower extremities. In capillaritis, there is an extravasation of erythrocytes as a result of perivascular lymphocytic inflammation. The petechiae are bright red, 1–2 mm in size, and scattered within yellow-brown patches. The yellow-brown color is caused by hemosiderin deposits within the dermis.

Systemic causes of nonpalpable purpura fall into several categories, and those secondary to clotting disturbances and vascular fragility will be discussed first. The former group includes thrombocytopenia (Chap. 115), abnormal platelet function as is seen in uremia, and clotting factor defects. The initial site of presentation for thrombocytopenia-induced petechiae is the distal lower extremity. Capillary fragility leads to nonpalpable purpura in patients with systemic amyloidosis (see “Papulonodular Skin Lesions,” above), disorders of collagen production such as Ehlers-Danlos syndrome, and scurvy. In scurvy, there are flattened corkscrew hairs with surrounding hemorrhage on the lower extremities, in addition to gingivitis. Vitamin C is a cofactor for lysyl hydroxylase, an enzyme involved in the posttranslational modification of procollagen that is necessary for cross-link formation.

In contrast to the previous group of disorders, the noninflammatory purpura seen in the following group of diseases are associated with thrombi formation within vessels and have a retiform configuration. It is important to note that these thrombi are demonstrable in skin biopsy specimens. This group of disorders includes disseminated intravascular coagulation (DIC), monoclonal cryoglobulinemia, thrombocytosis, thrombotic thrombocytopenic purpura, antiphospholipid antibody syndrome, and reactions to warfarin and heparin (heparin-induced thrombocytopenia and thrombosis). DIC is triggered by several types of infection (gram-negative, gram-positive, viral, and rickettsial) as well as by tissue injury and neoplasms. Widespread purpura and hemorrhagic infarcts of the distal extremities are seen. Similar lesions are found in purpura fulminans, which is a form of DIC associated with fever and hypotension that occurs more commonly in children following an infectious illness such as varicella, scarlet fever, or an upper respiratory tract infection. In both disorders, hemorrhagic bullae can develop in involved skin.

Monoclonal cryoglobulinemia is associated with plasma cell dyscrasias, chronic lymphocytic leukemia, and lymphoma. Purpura, primarily of the lower extremities, and hemorrhagic infarcts of the fingers, toes, nose and ears are seen in these patients. Exacerbations of disease activity can follow cold exposure or an increase in serum viscosity. Biopsy specimens show precipitates of the cryoglobulin within dermal vessels. Similar deposits have been found in the lung, brain, and renal glomeruli. Patients with thrombotic thrombocytopenic purpura can also have hemorrhagic infarcts as a result of intravascular thromboses. Additional signs include microangiopathic hemolytic anemia and fluctuating neurologic abnormalities, especially headaches and confusion.

Administration of warfarin can result in painful areas of erythema that become purpuric and then necrotic with an adherent black eschar; the condition is also referred to as Coumadin-induced necrosis. This reaction is seen more often in women and in areas with abundant subcutaneous fat—breasts, abdomen, buttocks, thighs, and calves. The erythema and purpura develop between the third and tenth day of therapy, most likely as a result of a transient imbalance in the levels of anticoagulant and procoagulant vitamin K–dependent factors. Continued therapy does not exacerbate preexisting lesions, and patients with an inherited or acquired deficiency of protein C are at increased risk for this particular reaction as well as for purpura fulminans and calciphylaxis.

Purpura secondary to cholesterol emboli are usually seen on the lower extremities of patients with atherosclerotic vascular disease. They often follow anticoagulant therapy or an invasive vascular procedure such as an arteriogram but also occur spontaneously from disintegration of atheromatous plaques. Associated findings include livedo reticularis, gangrene, cyanosis, and ischemic ulcerations. Multiple step sections of the biopsy specimen may be necessary to demonstrate the cholesterol clefts within the vessels. Petechiae are also an important sign of fat embolism and occur primarily on the upper body 2–3 days after a major injury. By using special fixatives, the emboli can be demonstrated in biopsy specimens of the petechiae. Rarely, emboli of tumor or thrombus are seen in patients with atrial myxomas and marantic endocarditis.

In the Gardner-Diamond syndrome (autoerythrocyte sensitivity), female patients develop large ecchymoses within areas of painful, warm erythema. Intradermal injections of autologous erythrocytes or phosphatidyl serine derived from the red cell membrane can reproduce the lesions in some patients; however, there are instances where a reaction is seen at an injection site of the forearm but not in the midback region. The latter has led some observers to view Gardner-Diamond syndrome as a cutaneous manifestation of severe emotional stress. More recently, the possibility of platelet dysfunction (as assessed via aggregation studies) has been raised. Waldenström’s hypergammaglobulinemic purpura is a chronic disorder characterized by recurrent crops of petechiae and larger purpuric macules on the lower extremities. There are circulating complexes of IgG–anti-IgG molecules, and exacerbations are associated with prolonged standing or walking. Patients may have an underlying autoimmune connective tissue disease, e.g., Sjögren’s syndrome.

Palpable purpura are further subdivided into vasculitic and embolic. In the group of vasculitic disorders, cutaneous small-vessel vasculitis, also known as leukocytoclastic vasculitis (LCV), is the one most commonly associated with palpable purpura (Chap. 363). Underlying etiologies include drugs (e.g., antibiotics), infections (e.g., hepatitis C virus), and autoimmune connective tissue diseases (e.g., rheumatoid arthritis, Sjögren’s syndrome, lupus). Henoch-Schönlein purpura (HSP) is a subtype of acute LCV that is seen more commonly in children and adolescents following an upper respiratory infection. The majority of lesions are found on the lower extremities and buttocks. Systemic manifestations include fever, arthralgias (primarily of the knees and ankles), abdominal pain, gastrointestinal bleeding, and nephritis. Direct immunofluorescence examination shows deposits of IgA within dermal blood vessel walls. Renal disease is of particular concern in adults with IgA vasculitis.

Several types of infectious emboli can give rise to palpable purpura. These embolic lesions are usually irregular in outline as opposed to the lesions of LCV, which are circular in outline. The irregular outline is indicative of a cutaneous infarct, and the size corresponds to the area of skin that received its blood supply from that particular arteriole or artery. The palpable purpura in LCV are circular because the erythrocytes simply diffuse out evenly from the postcapillary venules as a result of inflammation. Infectious emboli are most commonly due to gram-negative cocci (meningococcus, gonococcus), gram-negative rods (Enterobacteriaceae), and gram-positive cocci (Staphylococcus). Additional causes include Rickettsia and, in immunocompromised patients, Aspergillus and other opportunistic fungi.

The embolic lesions in acute meningococcemia are found primarily on the trunk, lower extremities, and sites of pressure, and a gunmetal-gray color often develops within them. Their size varies from a few millimeters to several centimeters, and the organisms can be cultured from the lesions. Associated findings include a preceding upper respiratory tract infection; fever; meningitis; DIC; and, in some patients, a deficiency of the terminal components of complement. In disseminated gonococcal infection (arthritis-dermatitis syndrome), a small number of inflammatory papules and vesicopustules, often with central purpura or hemorrhagic necrosis, are found on the distal extremities. Additional symptoms include arthralgias, tenosynovitis, and fever. To establish the diagnosis, a Gram stain of these lesions should be performed. Rocky Mountain spotted fever is a tick-borne disease that is caused by Rickettsia rickettsii. A several-day history of fever, chills, severe headache, and photophobia precedes the onset of the cutaneous eruption. The initial lesions are erythematous macules and papules on the wrists, ankles, palms, and soles. With time, the lesions spread centripetally and become purpuric.

Lesions of ecthyma gangrenosum begin as edematous, erythematous papules or plaques and then develop central purpura and necrosis. Bullae formation also occurs in these lesions, and they are frequently found in the girdle region. The organism that is classically associated with ecthyma gangrenosum is Pseudomonas aeruginosa, but other gram-negative rods such as Klebsiella, Escherichia coli, and Serratia can produce similar lesions. In immunocompromised hosts, the list of potential pathogens is expanded to include Candida and other opportunistic fungi (e.g., Aspergillus, Fusarium).

ULCERS

The approach to the patient with a cutaneous ulcer is outlined in Table 58-17. Peripheral vascular diseases of the extremities are reviewed in Chap. 281, as is Raynaud’s phenomenon.

Livedoid vasculopathy (livedoid vasculitis; atrophie blanche) represents a combination of a vasculopathy plus intravascular thrombosis. Purpuric lesions and livedo reticularis are found in association with painful ulcerations of the lower extremities. These ulcers are often slow to heal, but when they do, irregularly shaped white scars form. The majority of cases are secondary to venous hypertension, but possible underlying illnesses include disorders of hypercoagulability, for example, antiphospholipid syndrome and factor V Leiden (Chaps. 117 and 357).

In pyoderma gangrenosum, the border of untreated active ulcers has a characteristic appearance consisting of an undermined necrotic violaceous edge and a peripheral erythematous halo. The ulcers often begin as pustules that then expand rather rapidly to a size as large as 20 cm. Although these lesions are most commonly found on the lower extremities, they can arise anywhere on the surface of the body, including at sites of trauma (pathergy). An estimated 30–50% of cases are idiopathic, and the most common associated disorders are ulcerative colitis and Crohn’s disease. Less commonly, pyoderma gangrenosum is associated with seropositive rheumatoid arthritis, acute and chronic myelogenous leukemia, myelodysplasia, a monoclonal gammopathy (usually IgA), or an autoinflammatory disorder. Because the histology of pyoderma gangrenosum may be nonspecific (dermal infiltrate of neutrophils when in untreated state), the diagnosis requires clinicopathologic correlation, in particular, the exclusion of similar-appearing ulcers such as necrotizing vasculitis, Meleney’s ulcer (synergistic infection at a site of trauma or surgery), dimorphic fungi, cutaneous amebiasis, spider bites, and factitial. In the myeloproliferative disorders, the ulcers may be more superficial with a pustulobullous border, and these lesions provide a connection between classic pyoderma gangrenosum and acute febrile neutrophilic dermatosis (Sweet syndrome).

FEVER AND RASH

The major considerations in a patient with a fever and a rash are inflammatory diseases versus infectious diseases. In the hospital setting, the most common scenario is a patient who has a drug rash plus a fever secondary to an underlying infection. However, it should be emphasized that a drug reaction can lead to both a cutaneous eruption and a fever (“drug fever”), especially in the setting of DRESS, AGEP, or serum sickness–like reaction. Additional inflammatory diseases that are often associated with a fever include pustular psoriasis, erythroderma, and Sweet syndrome. Lyme disease, secondary syphilis, and viral and bacterial exanthems (see “Exanthems,” above) are examples of infectious diseases that produce a rash and a fever. Lastly, it is important to determine whether or not the cutaneous lesions represent septic emboli (see “Purpura,” above). Such lesions usually have evidence of ischemia in the form of purpura, necrosis, or impending necrosis (gunmetal-gray color). In the patient with thrombocytopenia, however, purpura can be seen in inflammatory reactions such as morbilliform drug eruptions and infectious lesions.

FURTHER READING

INTRODUCTION

A number of immunologically mediated skin diseases and immunologically mediated systemic disorders with cutaneous manifestations are now recognized as distinct entities with consistent clinical, histologic, and immunopathologic findings. Clinically, these disorders are characterized by morbidity (pain, pruritus, disfigurement) and, in some instances, result in death (largely due to loss of epidermal barrier function and/or secondary infection). The major features of the more common immunologically mediated skin diseases are summarized in this chapter (Table 59-1), as are autoimmune systemic disorders with cutaneous manifestations.

AUTOIMMUNE CUTANEOUS DISEASES

PEMPHIGUS VULGARIS

Pemphigus refers to a group of autoantibody-mediated intraepidermal blistering diseases characterized by loss of cohesion between epidermal cells (a process termed acantholysis). Manual pressure to the skin of these patients may elicit the separation of the epidermis (Nikolsky’s sign). This finding, while characteristic of pemphigus, is not specific to this group of disorders and is also seen in toxic epidermal necrolysis, Stevens-Johnson syndrome, and a few other skin diseases.

Pemphigus vulgaris (PV) is a mucocutaneous blistering disease that predominantly occurs in patients >40 years of age. PV typically begins on mucosal surfaces and often progresses to involve the skin. This disease is characterized by fragile, flaccid blisters that rupture to produce extensive denudation of mucous membranes and skin (Fig. 59-1). The mouth, scalp, face, neck, axilla, groin, and trunk are typically involved. PV may be associated with severe skin pain; some patients experience pruritus as well. Lesions usually heal without scarring except at sites complicated by secondary infection or mechanically induced dermal wounds. Postinflammatory hyperpigmentation is usually present for some time at sites of healed lesions.

Biopsies of early lesions demonstrate intraepidermal vesicle formation secondary to loss of cohesion between epidermal cells (i.e., acantholytic blisters). Blister cavities contain acantholytic epidermal cells, which appear as round homogeneous cells containing hyperchromatic nuclei. Basal keratinocytes remain attached to the epidermal basement membrane; hence, blister formation takes place within the suprabasal portion of the epidermis. Lesional skin may contain focal collections of intraepidermal eosinophils within blister cavities; dermal alterations are slight, often limited to an eosinophil-predominant leukocytic infiltrate. Direct immunofluorescence microscopy of lesional or intact patient skin shows deposits of IgG on the surface of keratinocytes; deposits of complement components are typically found in lesional but not in uninvolved skin. Deposits of IgG on keratinocytes are derived from circulating autoantibodies to cell-surface autoantigens. Such circulating autoantibodies can be demonstrated in 80–90% of PV patients by indirect immunofluorescence microscopy; monkey esophagus is the optimal substrate for these studies. Patients with PV have IgG autoantibodies to desmogleins (Dsgs), transmembrane desmosomal glycoproteins that belong to the cadherin family of calcium-dependent adhesion molecules. Such autoantibodies can be precisely quantitated by enzyme-linked immunosorbent assay (ELISA). Patients with early PV (i.e., mucosal disease) have IgG autoantibodies to Dsg3; patients with advanced PV (i.e., mucocutaneous disease) have IgG autoantibodies to both Dsg3 and Dsg1. Experimental studies have shown that autoantibodies from patients with PV are pathogenic (i.e., responsible for blister formation) and that their titer correlates with disease activity. Recent studies have shown that the anti-Dsg autoantibody profile in these patients’ sera as well as the tissue distribution of Dsg3 and Dsg1 determine the site of blister formation in patients with PV. Coexpression of Dsg3 and Dsg1 by epidermal cells protects against pathogenic IgG antibodies to either of these cadherins but not against pathogenic autoantibodies to both.

PV can be life-threatening. Prior to the availability of glucocorticoids, mortality rates ranged from 60% to 90%; the current figure is ~5%. Common causes of morbidity and death are infection and complications of treatment. Bad prognostic factors include advanced age, widespread involvement, and the requirement for high doses of glucocorticoids (with or without other immunosuppressive agents) for control of disease. The course of PV in individual patients is variable and difficult to predict. Some patients experience remission, while others may require long-term treatment or succumb to complications of their disease or its treatment. The mainstay of treatment is systemic glucocorticoids alone or in combination with other immunosuppressive agents. Patients with moderate to severe PV are usually started on prednisone at doses ≤1 mg/kg per day (single morning dose). If new lesions continue to appear after 1–2 weeks of treatment, the dose of prednisone may need to be increased and/or combined with another immunosuppressive agent. Among these, rituximab in combination with prednisone often achieves remission (though maintenance therapy may be required to prevent relapse). Other immunosuppressive agents sometimes combined with prednisone to treat PV include azathioprine, mycophenolate mofetil, or cyclophosphamide. Patients with severe, treatment-resistant disease may derive benefit from plasmapheresis (six high-volume exchanges [i.e., 2–3 L per exchange] over ~2 weeks) and/or IV immunoglobulin (IVIg). It is important to bring severe or progressive disease under control quickly in order to lessen the severity and/or duration of this disorder. Increasingly, rituximab and daily glucocorticoids are used early in PV patients to avert the development of advanced and/or treatment-resistant disease.

PEMPHIGUS FOLIACEUS

Pemphigus foliaceus (PF) is distinguished from PV by several features. In PF, acantholytic blisters are located high within the epidermis, usually just beneath the stratum corneum. Hence, PF is a more superficial blistering disease than PV. The distribution of lesions in the two disorders is much the same, except that in PF mucous membranes are almost always spared. Patients with PF rarely have intact blisters but rather exhibit shallow erosions associated with erythema, scale, and crust formation. Mild cases of PF can resemble severe seborrheic dermatitis; severe PF may cause extensive exfoliation. Sun exposure (ultraviolet irradiation) may be an aggravating factor.

PF has immunopathologic features in common with PV. Specifically, direct immunofluorescence microscopy of perilesional skin demonstrates IgG on the surface of keratinocytes. Similarly, patients with PF have circulating IgG autoantibodies directed against the surface of keratinocytes. In PF, autoantibodies are directed against Dsg1, a 160-kDa desmosomal cadherin. These autoantibodies can be quantitated by ELISA. As noted for PV, the autoantibody profile in patients with PF (i.e., anti-Dsg1 IgG) and the tissue distribution of this autoantigen (i.e., expression in oral mucosa that is compensated by coexpression of Dsg3) are thought to account for the distribution of lesions in this disease.

Endemic forms of PF are found in south-central rural Brazil, where the disease is known as fogo salvagem (FS), as well as in selected sites in Latin America and Tunisia. Endemic PF, like other forms of this disease, is mediated by IgG autoantibodies to Dsg1. Clusters of FS overlap with those of leishmaniasis, a disease transmitted by bites of the sand fly Lutzomyia longipalis. Studies have shown that sand fly salivary antigens (specifically, the LJM11 salivary protein) are recognized by IgG autoantibodies from FS patients (as well as by monoclonal antibodies to Dsg1 derived from these patients). The demonstration that mice immunized with LJM11 produce antibodies to Dsg1 suggests that insect bites may deliver salivary antigens, initiate a cross-reactive humoral immune response, and lead to FS in genetically susceptible individuals.

Although pemphigus has been associated with several autoimmune diseases, its association with thymoma and/or myasthenia gravis is particularly notable. To date, >30 cases of thymoma and/or myasthenia gravis have been reported in association with pemphigus, usually with PF. Patients may also develop pemphigus as a consequence of drug exposure; drug-induced pemphigus usually resembles PF rather than PV. Drugs containing a thiol group in their chemical structure (e.g., penicillamine, captopril, enalapril) are most commonly associated with drug-induced pemphigus. Nonthiol drugs linked to pemphigus include penicillins, cephalosporins, and piroxicam. Some cases of drug-induced pemphigus are durable and require treatment with systemic glucocorticoids and/or immunosuppressive agents.

PF is generally a less severe disease than PV and usually carries a better prognosis. Localized disease can sometimes be treated with topical or intralesional glucocorticoids; more active cases can usually be controlled with systemic glucocorticoids either alone or in combination with other immunosuppressive agents. Patients with severe, treatment-resistant disease may require more aggressive interventions, as described above for patients with PV.

PARANEOPLASTIC PEMPHIGUS

Paraneoplastic pemphigus (PNP) is an autoimmune acantholytic mucocutaneous disease associated with an occult or confirmed neoplasm. Patients with PNP typically have painful stomatitis in association with papulosquamous and/or lichenoid eruptions that often progress to blisters. Palm and sole involvement are common in these patients and raise the possibility that prior reports of neoplasia-associated erythema multiforme may have represented unrecognized cases of PNP. Biopsies of lesional skin from these patients show varying combinations of acantholysis, keratinocyte necrosis, and vacuolar-interface dermatitis. Direct immunofluorescence microscopy of a patient’s skin shows deposits of IgG and complement on the surface of keratinocytes and (variably) similar immunoreactants in the epidermal basement membrane zone. Patients with PNP have IgG autoantibodies to cytoplasmic proteins that are members of the plakin family (e.g., desmoplakins I and II, bullous pemphigoid antigen [BPAG] 1, envoplakin, periplakin, and plectin) and to cell-surface proteins that are members of the cadherin family (e.g., Dsg1 and Dsg3). Passive transfer studies have shown that autoantibodies from patients with PNP are pathogenic in animal models.

The predominant neoplasms associated with PNP are non-Hodgkin’s lymphoma, chronic lymphocytic leukemia, thymoma, spindle cell tumors, Waldenström’s macroglobulinemia, and Castleman’s disease; the last-mentioned neoplasm is particularly common among children with PNP. Rare cases of seronegative PNP have been reported in patients with B-cell malignancies previously treated with rituximab. In addition to severe skin lesions, many patients with PNP develop life-threatening bronchiolitis obliterans. PNP is generally resistant to conventional therapies (i.e., those used to treat PV); rarely, a patient’s disease may ameliorate or even remit following ablation or removal of underlying neoplasms.

BULLOUS PEMPHIGOID

Bullous pemphigoid (BP) is a polymorphic autoimmune subepidermal blistering disease usually seen in the elderly. Initial lesions may consist of urticarial plaques; most patients eventually display tense blisters on either normal-appearing or erythematous skin (Fig. 59-2). The lesions are usually distributed over the lower abdomen, groin, and flexor surface of the extremities; oral mucosal lesions are found in some patients. Pruritus may be nonexistent or severe. As lesions evolve, tense blisters tend to rupture and be replaced by erosions with or without surmounting crust. Nontraumatized blisters heal without scarring. The major histocompatibility complex class II allele HLA-DQβ1^*0301 is prevalent in patients with BP. Though most cases occur sporadically, BP can be triggered by medications (e.g., furosemide, dipeptidyl peptidase-4 inhibitors, immune checkpoint inhibitors), ultraviolet light, or ionizing radiation. Several studies have shown that BP is associated with neurologic diseases (e.g., stroke, dementia, Parkinson’s disease, and multiple sclerosis).

Biopsies of early lesional skin demonstrate subepidermal blisters and histologic features that roughly correlate with the clinical character of the lesion under study. Lesions on normal-appearing skin generally contain a sparse perivascular leukocytic infiltrate with some eosinophils; conversely, biopsies of inflammatory lesions typically show an eosinophil-rich infiltrate at sites of vesicle formation and in perivascular areas. In addition to eosinophils, cell-rich lesions also contain mononuclear cells and neutrophils. It is not possible to distinguish BP from other subepidermal blistering diseases by routine histologic studies alone.

Direct immunofluorescence microscopy of normal-appearing perilesional skin from patients with BP shows linear deposits of IgG and/or C3 in the epidermal basement membrane. The sera of ~70% of these patients contain circulating IgG autoantibodies that bind the epidermal basement membrane of normal human skin in indirect immunofluorescence microscopy. IgG from an even higher percentage of patients reacts with the epidermal side of 1 M NaCl split skin (an alternative immunofluorescence microscopy test substrate used to distinguish circulating IgG autoantibodies to the basement membrane in patients with BP from those in patients with similar, yet different, subepidermal blistering diseases; see below). In BP, circulating autoantibodies recognize 230- and 180-kDa hemidesmosome-associated proteins in basal keratinocytes (i.e., BPAG1 and BPAG2, respectively). Autoantibodies to BPAG2 are thought to deposit in situ, activate complement, produce dermal mast-cell degranulation, and generate granulocyte-rich infiltrates that cause tissue damage and blister formation.

BP may persist for months to years, with exacerbations or remissions. Extensive involvement may result in widespread erosions and compromise cutaneous integrity; elderly and/or debilitated patients may die. Local or minimal disease can sometimes be controlled with potent topical glucocorticoids alone; more extensive lesions generally respond to systemic glucocorticoids either alone or in combination with other agents. Adjuncts to systemic glucocorticoids include doxycycline, azathioprine, mycophenolate mofetil, and rituximab.

PEMPHIGOID GESTATIONIS

Pemphigoid gestationis (PG), also known as herpes gestationis, is a rare, nonviral, subepidermal blistering disease of pregnancy and the puerperium. PG may begin during any trimester of pregnancy or present shortly after delivery. Lesions are usually distributed over the abdomen, trunk, and extremities; mucous membrane lesions are rare. Skin lesions in these patients may be quite polymorphic and consist of erythematous urticarial papules and plaques, vesiculopapules, and/or frank bullae. Lesions are almost always extremely pruritic. Severe exacerbations of PG frequently follow delivery, typically within 24–48 h. PG tends to recur in subsequent pregnancies, often beginning earlier during such gestations. Brief flare-ups of disease may occur with resumption of menses and may develop in patients later exposed to oral contraceptives. Occasionally, infants of affected mothers have transient skin lesions.

Biopsies of early lesional skin show teardrop-shaped subepidermal vesicles forming in dermal papillae in association with an eosinophil-rich leukocytic infiltrate. Differentiation of PG from other subepidermal bullous diseases by light microscopy is difficult. However, direct immunofluorescence microscopy of perilesional skin from PG patients reveals the immunopathologic hallmark of this disorder: linear deposits of C3 in the epidermal basement membrane. These deposits develop as a consequence of complement activation produced by low-titer IgG anti–basement membrane autoantibodies directed against BPAG2, the same hemidesmosome-associated protein that is targeted by autoantibodies in patients with BP—a subepidermal bullous disease that resembles PG clinically, histologically, and immunopathologically.

The goals of therapy in patients with PG are to prevent the development of new lesions, relieve intense pruritus, and care for erosions at sites of blister formation. Many patients require treatment with moderate doses of daily glucocorticoids (i.e., 20–40 mg of prednisone) at some point in their course. Mild cases (or brief flare-ups) may be controlled by vigorous use of potent topical glucocorticoids. Infants born of mothers with PG appear to be at increased risk of being born slightly premature or “small for dates.” Current evidence suggests that there is no difference in the incidence of uncomplicated live births between PG patients treated with systemic glucocorticoids and those managed more conservatively. If systemic glucocorticoids are administered, newborns are at risk for development of reversible adrenal insufficiency.

DERMATITIS HERPETIFORMIS

Dermatitis herpetiformis (DH) is an intensely pruritic, papulovesicular skin disease characterized by lesions symmetrically distributed over extensor surfaces (i.e., elbows, knees, buttocks, back, scalp, and posterior neck) (see Fig. 56-8). Primary lesions in this disorder consist of papules, papulovesicles, or urticarial plaques. Because pruritus is prominent, patients may present with excoriations and crusted papules but no observable primary lesions. Patients sometimes report that their pruritus has a distinctive burning or stinging component; the onset of such local symptoms reliably heralds the development of distinct clinical lesions 12–24 h later. Almost all DH patients have associated, usually subclinical, gluten-sensitive enteropathy (Chap. 325), and >90% express the HLA-B8/DRw3 and HLA-DQw2 haplotypes. DH may present at any age, including in childhood; onset in the second to fourth decades is most common. The disease is typically chronic.

Biopsy of early lesional skin reveals neutrophil-rich infiltrates within dermal papillae. Neutrophils, fibrin, edema, and microvesicle formation at these sites are characteristic of early disease. Older lesions may demonstrate nonspecific features of a subepidermal bulla or an excoriated papule. Because the clinical and histologic features of this disease can be variable and resemble those of other subepidermal blistering disorders, the diagnosis is confirmed by direct immunofluorescence microscopy of normal-appearing perilesional skin. Such studies demonstrate granular deposits of IgA (with or without complement components) in the papillary dermis and along the epidermal basement membrane zone. IgA deposits in the skin are unaffected by control of disease with medication; however, these immunoreactants diminish in intensity or disappear in patients maintained for long periods on a strict gluten-free diet (see below). Patients with DH have granular deposits of IgA in their epidermal basement membrane zone and should be distinguished from individuals with linear IgA deposits at this site (see below).

Although most DH patients do not report overt gastrointestinal symptoms or have laboratory evidence of malabsorption, biopsies of the small bowel usually reveal blunting of intestinal villi and a lymphocytic infiltrate in the lamina propria. As is true for patients with celiac disease, this gastrointestinal abnormality can be reversed by a gluten-free diet. Moreover, if maintained, this diet alone may control the skin disease and eventuate in clearance of IgA deposits from these patients’ epidermal basement membrane zones. Subsequent gluten exposure in such patients alters the morphology of their small bowel, elicits a flare-up of their skin disease, and is associated with the reappearance of IgA in their epidermal basement membrane zones. As in patients with celiac disease, dietary gluten sensitivity in patients with DH is associated with IgA anti-endomysial autoantibodies that target tissue transglutaminase. Studies indicate that patients with DH also have high-avidity IgA autoantibodies to epidermal transglutaminase and that the latter is co-localized with granular deposits of IgA in the papillary dermis of DH patients. Patients with DH also have an increased incidence of thyroid abnormalities, achlorhydria, atrophic gastritis, and autoantibodies to gastric parietal cells. These associations likely relate to the high frequency of the HLA-B8/DRw3 haplotype in these patients, since this marker is commonly linked to autoimmune disorders. The mainstay of treatment of DH is dapsone, a sulfone. Patients respond rapidly (24–48 h) to dapsone, but require careful pretreatment evaluation (e.g., screening for glucose-6-phosphate dehydrogenase deficiency) and close follow-up to ensure that complications are avoided or controlled. All patients taking dapsone at >100 mg/d will have some hemolysis and methemoglobinemia, which are expected pharmacologic side effects of this agent. Gluten restriction can control DH and lessen dapsone requirements; this diet must rigidly exclude gluten to be of maximal benefit. Many months of dietary restriction may be necessary before a beneficial result is achieved. Good dietary counseling by a trained dietitian is essential.

LINEAR IgA DISEASE

Linear IgA disease, once considered a variant form of DH, is actually a separate and distinct entity. Clinically, patients with linear IgA disease may resemble individuals with DH, BP, or other subepidermal blistering diseases. Lesions typically consist of papulovesicles, bullae, and/or urticarial plaques that develop predominantly on central or flexural sites. Oral mucosal involvement occurs in some patients. Severe pruritus resembles that seen in patients with DH. Patients with linear IgA disease do not have an increased frequency of the HLA-B8/DRw3 haplotype or an associated enteropathy and therefore are not candidates for treatment with a gluten-free diet.

Histologic alterations in early lesions may be virtually indistinguishable from those in DH. However, direct immunofluorescence microscopy of normal-appearing perilesional skin reveals a linear band of IgA (and often C3) in the epidermal basement membrane zone. Most patients with linear IgA disease have circulating IgA anti-basement membrane autoantibodies directed against neoepitopes in the proteolytically processed extracellular domain of BPAG2. These patients generally respond to treatment with dapsone (50–200 mg/d) alone or in combination with low daily doses of prednisone.

EPIDERMOLYSIS BULLOSA ACQUISITA

Epidermolysis bullosa acquisita (EBA) is a rare, noninherited, polymorphic, chronic, subepidermal blistering disease. (The inherited form is discussed in Chap. 413.) Patients with classic or noninflammatory EBA have blisters on noninflamed skin, atrophic scars, milia, nail dystrophy, hair loss, and oral lesions. Because lesions generally occur at sites exposed to minor trauma, classic EBA is considered a mechanobullous disease. Other patients with EBA have widespread inflammatory scarring and bullous lesions that resemble severe BP. Inflammatory EBA may evolve into the classic, noninflammatory form of this disease. Rarely, patients present with lesions that predominate on mucous membranes. The HLA-DR2 haplotype is found with increased frequency in EBA patients. Studies suggest that EBA is sometimes associated with inflammatory bowel disease (especially Crohn’s disease).

The histology of lesional skin varies with the character of the lesion being studied. Noninflammatory bullae are subepidermal, feature a sparse leukocytic infiltrate, and resemble the lesions in patients with porphyria cutanea tarda. Inflammatory lesions consist of neutrophil-rich subepidermal blisters. EBA patients have continuous deposits of IgG (and frequently C3) in a linear pattern within the epidermal basement membrane zone. Ultrastructurally, these immunoreactants are found in the sublamina densa region in association with anchoring fibrils. Approximately 50% of EBA patients have demonstrable circulating IgG anti-basement membrane autoantibodies directed against type VII collagen—the collagen species that makes up anchoring fibrils. Such IgG autoantibodies bind the dermal side of 1 M NaCl split skin (in contrast to IgG autoantibodies in patients with BP). Studies have shown that passive transfer of experimental or patient IgG against type VII collagen can produce lesions in mice that clinically, histologically, and immunopathologically resemble those in patients with EBA.

Treatment of EBA is generally unsatisfactory. Some patients with inflammatory EBA may respond to systemic glucocorticoids, either alone or in combination with immunosuppressive agents. Other patients (especially those with neutrophil-rich inflammatory lesions) may respond to dapsone. The chronic, noninflammatory form of EBA is largely resistant to treatment, although some patients may respond to prednisone in combination with rituximab, cyclosporine, mycophenolate mofetil, azathioprine, or IVIg.

MUCOUS MEMBRANE PEMPHIGOID

Mucous membrane pemphigoid (MMP) is a rare, acquired, subepithelial immunobullous disease characterized by erosive lesions of mucous membranes and skin that result in scarring of at least some sites of involvement. Common sites include the oral mucosa (especially the gingiva) and conjunctiva; other sites that may be affected include the nasopharyngeal, laryngeal, esophageal, and anogenital mucosa. Skin lesions (present in about one-third of patients) tend to predominate on the scalp, face, and upper trunk and generally consist of a few scattered erosions or tense blisters on an erythematous or urticarial base. MMP is typically a chronic and progressive disorder. Serious complications may arise as a consequence of ocular, laryngeal, esophageal, or anogenital lesions. Erosive conjunctivitis may result in shortened fornices, symblepharon, ankyloblepharon, entropion, corneal opacities, and (in severe cases) blindness. Similarly, erosive lesions of the larynx may cause hoarseness, pain, and tissue loss that, if unrecognized and untreated, may eventuate in complete destruction of the airway. Esophageal lesions may result in stenosis and/or strictures that could place patients at risk for aspiration. Strictures may also complicate anogenital involvement.

Biopsies of lesional tissue generally show subepithelial vesiculobullae and a mononuclear leukocytic infiltrate. Neutrophils and eosinophils may be seen in biopsies of early lesions; older lesions may demonstrate a scant leukocytic infiltrate and fibrosis. Direct immunofluorescence microscopy of perilesional tissue typically reveals deposits of IgG, IgA, and/or C3 in the epidermal basement membrane. Because many patients with MMP exhibit no evidence of circulating anti-basement membrane autoantibodies, testing of perilesional skin is important diagnostically. Although MMP was once thought to be a single nosologic entity, it is now largely regarded as a disease phenotype that may develop as a consequence of an autoimmune reaction to a variety of molecules in the epidermal basement membrane (e.g., BPAG2, laminin-332, type VII collagen, α₆β₄ integrin) and other antigens yet to be completely defined. Studies suggest that MMP patients with autoantibodies to laminin-332 have an increased relative risk for cancer. Treatment of MMP is largely dependent upon the sites of involvement. Due to potentially severe complications, patients with ocular, laryngeal, esophageal, and/or anogenital involvement require aggressive systemic treatment with dapsone, prednisone, or the latter in combination with another immunosuppressive agent (e.g., rituximab, azathioprine, mycophenolate mofetil, or cyclophosphamide), or IVIg. Less threatening forms of the disease may be managed with topical or intralesional glucocorticoids.

AUTOIMMUNE SYSTEMIC DISEASES WITH PROMINENT CUTANEOUS FEATURES

DERMATOMYOSITIS

The cutaneous manifestations of dermatomyositis (Chap. 365) are often distinctive but at times may resemble those of systemic lupus erythematosus (SLE) (Chap. 356), scleroderma (Chap. 360), or other overlapping connective tissue diseases (Chap. 360). The extent and severity of cutaneous disease may or may not correlate with the extent and severity of the myositis. The cutaneous manifestations of dermatomyositis are similar, whether the disease appears in children or in the elderly, except that calcification of subcutaneous tissue is a common late sequela in childhood dermatomyositis. Dermatomyositis may be associated with interstitial lung disease or cancer.

The cutaneous signs of dermatomyositis may precede or follow the development of myositis by weeks to years. Cases lacking muscle involvement (i.e., dermatomyositis sine myositis or amyopathic dermatomyositis) have also been reported. The most common manifestation is a purple-red discoloration of the upper eyelids, sometimes associated with scaling (“heliotrope” erythema; Fig. 59-3) and periorbital edema. Erythema on the cheeks and nose in a “butterfly” distribution may resemble the malar eruption of SLE. Erythematous or violaceous thin, scaly plaques are common on the upper trunk and neck (shawl sign), the scalp, lateral aspects of the thighs (holster sign), and the extensor surfaces of the forearms and hands (tendon streaking). Approximately one-third of patients have violaceous, flat-topped papules over the dorsal interphalangeal joints that are pathognomonic of dermatomyositis (Gottron’s papules) (Fig. 59-4). Thin violaceous papules and plaques on the elbows and knees of patients with dermatomyositis are referred to as Gottron’s sign. These lesions can be contrasted with the erythema and scaling on the dorsum of the fingers that spares the skin over the interphalangeal joints of some SLE patients. Periungual telangiectasias and edema may be prominent in patients with dermatomyositis. Other patients, particularly those with long-standing disease, develop areas of hypopigmentation, hyperpigmentation, mild atrophy, and telangiectasia known as poikiloderma. Poikiloderma is rare in both SLE and scleroderma and thus can serve as a clinical sign that distinguishes dermatomyositis from these two diseases. Cutaneous changes may be similar in dermatomyositis and various overlap syndromes where thickening and binding down of the skin of the hands (sclerodactyly) as well as Raynaud’s phenomenon can be seen. However, the presence of severe muscle disease, Gottron’s papules, heliotrope erythema, and poikiloderma serves to distinguish patients with dermatomyositis. Skin biopsy of the erythematous, scaling lesions of dermatomyositis may reveal only mild nonspecific inflammation, but sometimes may show changes indistinguishable from those found in cutaneous lupus erythematosus (LE), including epidermal atrophy, hydropic degeneration of basal keratinocytes, and dermal changes consisting of interstitial mucin deposition and a mild mononuclear cell perivascular infiltrate. Direct immunofluorescence microscopy of lesional skin is usually negative, although granular deposits of immunoglobulin(s) and complement in the epidermal basement membrane zone have been described in some patients. Treatment should be stratified based on the relative severity of disease. Topical treatments include glucocorticoids, sunscreens, and aggressive photoprotective measures. Treatment of systemic disease includes antimalarials (though some patients may develop a drug eruption upon initiation of therapy) or systemic glucocorticoids in conjunction with methotrexate, mycophenolate mofetil, azathioprine, rituximab, or IVIg.

LUPUS ERYTHEMATOSUS

The cutaneous manifestations of LE (Chap. 356) can be divided into acute, subacute, and chronic types. Acute cutaneous LE is characterized by erythema of the nose and malar eminences in a “butterfly” distribution (Fig. 59-5A). The erythema is often sudden in onset, accompanied by edema and fine scale, and correlated with systemic involvement. Patients may have widespread involvement of the face as well as erythema and scaling of the extensor surfaces of the extremities and upper chest (Fig. 59-5B). These acute lesions, while sometimes evanescent, usually last for days and are often associated with exacerbations of systemic disease. Skin biopsy of acute lesions typically shows hydropic degeneration of basal keratinocytes, dermal edema, and (in some cases) a sparse perivascular infiltrate of mononuclear cells in the upper dermis as well as dermal mucin. Direct immunofluorescence microscopy of lesional skin frequently reveals deposits of immunoglobulin(s) and complement in the epidermal basement membrane zone. Treatment of cutaneous disease includes topical glucocorticoids, aggressive photoprotection, antimalarials, and control of systemic disease. Treatment of systemic disease associated with acute cutaneous LE includes systemic glucocorticoids in conjunction with other immunosuppressive agents.

Subacute cutaneous lupus erythematosus (SCLE) is characterized by a widespread photosensitive, nonscarring eruption. In most patients, renal and central nervous system involvement is mild or absent. SCLE may present as a papulosquamous eruption that resembles psoriasis or as annular polycyclic lesions. In the papulosquamous form, discrete erythematous papules arise on the back, chest, shoulders, extensor surfaces of the arms, and dorsum of the hands; lesions are uncommon on the central face and the flexor surfaces of the arms as well as below the waist. These slightly scaling papules tend to merge into plaques. The annular form involves the same areas and presents with erythematous papules that evolve into oval, circular, or polycyclic lesions. The lesions of SCLE are more widespread but have less tendency for scarring than lesions of discoid LE. In many patients with SCLE, drugs (e.g., hydrochlorothiazide, calcium channel blockers, antifungals, proton pump inhibitors) may induce or exacerbate disease. Skin biopsy typically reveals epidermal changes that include atrophy, hydropic degeneration of basal keratinocytes, and apoptosis accompanied by an infiltrate of mononuclear cells in the upper dermis. Direct immunofluorescence microscopy of lesional skin reveals deposits of immunoglobulin(s) in the epidermal basement membrane zone in about one-half of these cases. A particulate pattern of IgG deposition throughout the epidermis has been associated with SCLE. Most SCLE patients have anti-Ro autoantibodies. Local therapy alone is usually unsuccessful. Most patients require treatment with aminoquinoline antimalarial drugs. Low-dose therapy with oral glucocorticoids is sometimes necessary. Photoprotective measures against both ultraviolet B and ultraviolet A wavelengths are very important.

Chronic cutaneous LE has multiple subtypes; discoid LE (DLE) is the most common. DLE is characterized by discrete lesions, most often found on the face, scalp, and/or external ears. The lesions are erythematous papules or plaques with a thick, adherent scale that occludes hair follicles (follicular plugging). When the scale is removed, its underside shows small excrescences that correlate with the openings of hair follicles (so-called “carpet tacking”), a finding relatively specific for DLE. Long-standing lesions develop central atrophy, scarring, and hypopigmentation but frequently have erythematous, sometimes raised borders (Fig. 59-6). These lesions persist for years and tend to expand slowly. Up to 20% of patients with DLE eventually meet the American College of Rheumatology criteria for SLE. Typical discoid lesions are frequently seen in patients with SLE. Biopsy of DLE lesions shows hyperkeratosis, follicular plugging, atrophy of the epidermis, hydropic degeneration of basal keratinocytes, thickening of the epidermal basement membrane zone, and a mononuclear cell infiltrate adjacent to epidermal, adnexal, and microvascular basement membranes. Direct immunofluorescence microscopy demonstrates immunoglobulin(s) and complement deposits at the basement membrane zone in ~90% of cases. Treatment is focused on control of local cutaneous disease and consists mainly of photoprotection and topical or intralesional glucocorticoids. If local therapy is ineffective, use of aminoquinoline antimalarial agents may be indicated.

SCLERODERMA AND MORPHEA

The skin changes of scleroderma (Chap. 360) may be limited or diffuse. In both instances, disease usually begin on the fingers, hands, toes, feet, and face, with episodes of recurrent nonpitting edema. Sclerosis of the skin commences distally on the fingers (sclerodactyly) and spreads proximally, usually accompanied by resorption of bone of the fingertips, which may have punched out ulcers, stellate scars, or areas of hemorrhage (Fig. 59-7). The fingers may shrink and become sausage-shaped, and, because the fingernails are usually unaffected, they may curve over the end of the fingertips. Periungual telangiectasias are usually present, but periungual erythema is rare. In diffuse disease, the extremities show contractures and calcinosis cutis; facial involvement includes a smooth, unwrinkled brow, taut skin over the nose, shrinkage of tissue around the mouth, and perioral radial furrowing (Fig. 59-8). Matlike telangiectasias are often present, particularly on the face and hands. Involved skin feels indurated, smooth, and bound to underlying structures; hyper- and hypopigmentation are common as well. Raynaud’s phenomenon (i.e., cold-induced blanching, cyanosis, and reactive hyperemia) is documented in almost all patients and can precede development of scleroderma by many years. The combination of calcinosis cutis, Raynaud’s phenomenon, esophageal dysmotility, sclerodactyly, and telangiectasias has been termed as the CREST syndrome. Anti-centromere autoantibodies have been reported in a very high percentage of patients with CREST syndrome but in only a small minority of patients with scleroderma. Skin biopsy reveals thickening of the dermis, homogenization of collagen bundles, atrophic pilosebaceous and eccrine glands, and a sparse mononuclear cell infiltrate in the dermis and subcutaneous fat. Direct immunofluorescence microscopy of lesional skin is usually negative. Treatments for cutaneous disease include emollients, antipruritics, and phototherapy (UVA1 [ultraviolet A1 irradiation] or PUVA [psoralens + ultraviolet A irradiation]). Treatment of systemic disease includes vascular modifying agents, immunosuppressives, and antifibrotics.

Morphea is characterized by localized thickening and sclerosis of skin; it dominates on the trunk. This disorder may affect children or adults. Morphea begins as erythematous or flesh-colored plaques that become sclerotic, develop central hypopigmentation, and have an erythematous border. In most cases, patients have one or a few lesions, and the disease is termed circumscribed morphea. In some patients, widespread cutaneous lesions may occur without systemic involvement (generalized morphea). Many adults with generalized morphea have concomitant rheumatic or other autoimmune disorders. Skin biopsy of morphea is generally indistinguishable from that of scleroderma. Scleroderma and morphea are usually quite resistant to therapy. For this reason, physical therapy to prevent joint contractures and to maintain function is employed and is often helpful. Treatment options for early, rapidly progressive disease include phototherapy (UVA1 or PUVA) or methotrexate alone or in combination with daily glucocorticoids.

Diffuse fasciitis with eosinophilia is a clinical entity that can sometimes be confused with scleroderma. There is usually a sudden onset of swelling, induration, and erythema of the extremities, frequently following significant physical exertion, initiation of hemodialysis, exposure to certain medications, or other triggers. The proximal portions of the extremities (upper arms, forearms, thighs, calves) are more often involved than are the hands and feet. While the skin is indurated, it usually displays a woody, dimpled, or “pseudocellulite” appearance rather than being bound down as in scleroderma; contractures may occur early secondary to fascial involvement. The latter may also cause muscle groups to be separated and veins to appear depressed (i.e., the “groove sign”). These skin findings are accompanied by peripheral-blood eosinophilia, increased erythrocyte sedimentation rate, and sometimes hypergammaglobulinemia. Deep biopsy of affected areas of skin reveals inflammation and thickening of the deep fascia overlying muscle. An inflammatory infiltrate composed of eosinophils and mononuclear cells is usually found. Patients with eosinophilic fasciitis appear to be at increased risk for developing bone marrow failure or other hematologic abnormalities. While the ultimate course of eosinophilic fasciitis is variable, most patients respond favorably to treatment with prednisone. Relapses may occur and require treatment with prednisone in combination with other immunosuppressive or immunomodulatory agents.

The eosinophilia-myalgia syndrome, a disorder with epidemic numbers of cases reported in 1989 and linked to ingestion of L-tryptophan manufactured by a single company in Japan, is a multisystem disorder characterized by debilitating myalgias and absolute eosinophilia in association with varying combinations of arthralgias, pulmonary symptoms, and peripheral edema. In a later phase (3–6 months after initial symptoms), these patients often develop localized sclerodermatous skin changes, weight loss, and/or neuropathy (Chap. 360).

FURTHER READING

INTRODUCTION

Cutaneous reactions are the most frequent adverse reactions to medications, representing 10–15% of reported adverse drug reactions. Most are benign, but a few can be life threatening. Prompt recognition of severe reactions, drug withdrawal, and appropriate therapeutic interventions can minimize toxicity. This chapter focuses on adverse cutaneous reactions to systemic medications; it covers their incidence, patterns, and pathogenesis, and provides some practical guidelines on treatment, assessment of causality, and future use of drugs.

USE OF PRESCRIPTION DRUGS IN THE UNITED STATES

In the United States, more than 4 billion prescriptions for >60,000 drug products are dispensed annually. Hospital inpatients alone annually receive about 120 million courses of drug therapy, and half of adult Americans receive prescription drugs on a regular outpatient basis. Adverse effects of a prescription medication may result in 4.5 million urgent or emergency care visits and over 7000 deaths each year in the United States. Many patients use over-the-counter medicines that may cause adverse cutaneous reactions.

INCIDENCE OF CUTANEOUS REACTIONS

Several recent prospective studies reported that acute cutaneous reactions to drugs affect between 2.2 and 10 per 1000 hospitalized patients. Reactions usually occur a few days to 4 weeks after initiation of therapy.

In a series of 48,005 inpatients over a 20-year period, morbilliform rash (91%) and urticaria (6%) were the most frequent skin reactions, and antimicrobials, radiocontrast, and nonsteroidal anti-inflammatory drugs (NSAIDs) were the most common drug associations. Severe hypersensitivity reactions to medications have been reported to occur in between 1 in 1000 to 2 per million users, depending on the reaction type. Although rare, severe cutaneous reactions to drugs have an important impact on health because of significant sequelae; in addition, they may require hospitalization, increase the duration of hospital stay, or be life threatening. Some populations are at increased risk of drug reactions, including elderly patients, patients with autoimmune disease, hematopoietic stem cell transplant recipients, and those with acute Epstein-Barr virus (EBV) or human immunodeficiency virus (HIV) infection. The pathophysiology underlying this association is unknown but may be related to immune dysregulation. Individuals with advanced HIV disease (e.g., CD4 T lymphocyte count <200 cells/μL) have a 40- to 50-fold increased risk of adverse reactions to sulfamethoxazole (Chap. 202) and increased risk of severe hypersensitivity reactions.

In addition to acute eruptions, a variety of skin diseases can be induced or exacerbated by prolonged use of drugs (e.g., pruritus, pigmentation, nail or hair disorders, psoriasis, bullous pemphigoid, photosensitivity, and even cutaneous neoplasms). These drug reactions are not frequent; however, neither their incidence nor their impact on public health has been evaluated.

PATHOGENESIS OF DRUG REACTIONS

Adverse cutaneous responses to drugs can arise as a result of immunologic or nonimmunologic mechanisms.

NONIMMUNOLOGIC DRUG REACTIONS

Examples of nonimmunologic drug reactions are pigmentary changes due to dermal accumulation of medications or their metabolites, alteration of hair follicles by antimetabolites and signaling inhibitors, and lipodystrophy associated with metabolic effects of anti-HIV medications. These side effects are predictable and sometimes can be prevented.

IMMUNOLOGIC DRUG REACTIONS

Evidence suggests an immunologic basis for most acute drug eruptions. Drug reactions may result from immediate release of preformed mediators (e.g., urticaria, anaphylaxis), antibody-mediated reactions, immune complex deposition, and antigen-specific responses. Drug-specific CD4+ and CD8+ T-cell clones can be derived from the blood or from skin lesions of patients with a variety of drug allergies, strongly suggesting that these T cells mediate drug allergy in an antigen-specific manner. Drug presentation to T cells is major histocompatibility complex (MHC)-restricted and likely involves drug-peptide complex recognition by specific T-cell receptors (TCRs).

Once a drug has induced an immune response, the phenotype of the reaction is determined by the nature of effectors: cytotoxic (CD8+) T cells in blistering and certain hypersensitivity reactions, chemokines for reactions mediated by neutrophils or eosinophils, and B cell collaboration for production of specific antibodies for urticarial reactions. Immunologic reactions have recently been classified into further subtypes that provide a useful framework for designating adverse drug reactions based on involvement of specific immune pathways (Table 60-1).

Immediate Reactions

Immediate reactions depend on the release of mediators of inflammation by tissue mast cells or circulating basophils. These mediators include histamine, leukotrienes, prostaglandins, bradykinins, platelet-activating factor, enzymes, and proteoglycans. Drugs can trigger mediator release either directly (“anaphylactoid” reaction) or through IgE-specific antibodies. These reactions usually manifest in the skin and gastrointestinal, respiratory, and cardiovascular systems (Chap. 353). Primary symptoms and signs include pruritus, urticaria, nausea, vomiting, abdominal cramps, bronchospasm, laryngeal edema, and, occasionally, anaphylactic shock with hypotension and death. They occur within minutes of drug exposure. NSAIDs, including aspirin, and radiocontrast media are frequent causes of direct mast cell degranulation or anaphylactoid reactions, which can occur on first exposure. Penicillins and muscle relaxants used in general anesthesia are the most frequent causes of IgE-dependent reactions to drugs, which require prior sensitization. Release of mediators is triggered when polyvalent drug protein conjugates cross-link IgE molecules fixed to sensitized cells. Certain routes of administration favor different clinical patterns (e.g., gastrointestinal effects from oral route, circulatory effects from intravenous route).

Immune Complex–Dependent Reactions

Serum sickness is produced by tissue deposition of circulating immune complexes with consumption of complement. It is characterized by fever, arthritis, nephritis, neuritis, edema, and an urticarial, papular, or purpuric rash (Chap. 363). First described following administration of nonhuman sera, it currently occurs in the setting of monoclonal antibodies and similar medications. In classic serum sickness, symptoms develop 6 or more days after drug exposure, the latent period representing the time needed to synthesize antibody. Vasculitis, a relatively rare complication of drugs, may also be a result of immune complex deposition (Chap. 363). Penicillin, cefaclor, amoxicillin, trimethoprim/sulfamethoxazole, and monoclonal antibodies such as infliximab, rituximab, and omalizumab may be associated with clinically similar “serum sickness–like” reactions (SSLR). The mechanism of this reaction is unknown but is unrelated to immune complex formation and complement activation, and systemic involvement is rare. Whereas serum sickness most commonly occurs in adults, SSLR is more frequently observed in children.

Delayed Hypersensitivity

While not completely understood, delayed hypersensitivity directed by drug-specific T cells is an important mechanism underlying the most common drug eruptions, that is, morbilliform eruptions, and also rare and severe forms such as drug-induced hypersensitivity syndrome (DIHS) (also known as drug rash with eosinophilia and systemic symptoms [DRESS]), acute generalized exanthematous pustulosis (AGEP), Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN) (Table 60-1). Drug-specific T cells have been detected in these types of drug eruptions. In TEN, skin lesions contain T lymphocytes reactive to autologous lymphocytes and keratinocytes in a drug-specific, human leukocyte antigen (HLA)-restricted, and perforin/granzyme-mediated pathway. In the case of carbamazepine, studies have identified cytotoxic T lymphocytes (CTLs) reactive to carbamazepine that use highly restricted V-alpha and V-beta TCR repertoires in patients with carbamazepine hypersensitivity that are not found in carbamazepine-tolerant individuals.

The mechanism(s) by which medications result in T-cell activation is unknown. Two hypotheses prevail: first, that the antigens driving these reactions may be the native drug itself or components of the drug covalently complexed with endogenous proteins, presented in association with HLA molecules to T cells through the classic antigen presentation pathway or, alternatively, through direct interaction of the drug/metabolite with the TCR or peptide-loaded HLA (e.g., the pharmacologic interaction of drugs with immune receptors, or p-i hypothesis). Recent x-ray crystallography data characterizing binding between specific HLA molecules to drugs known to cause hypersensitivity reactions demonstrate unique alterations to the MHC peptide-binding groove, suggesting a molecular basis for T-cell activation in the development of hypersensitivity reactions.

GENETIC FACTORS AND CUTANEOUS DRUG REACTIONS

Genetic determinants may predispose individuals to severe drug reactions by affecting either drug metabolism or immune responses to drugs. Polymorphisms in cytochrome P450 enzymes, drug acetylation, methylation (such as thiopurine methyltransferase activity and azathioprine), and other forms of metabolism (such as glucose-6-phosphate dehydrogenase and dapsone) may increase susceptibility to drug toxicity or underdosing and increase risk for medication interactions, highlighting a role for differential pharmacokinetic or pharmacodynamic effects. The value of routine screening of P450 enzymes for prediction of cutaneous reactions has not been determined, though its cost-effectiveness in certain populations (e.g., patients with seizure disorder, depression) as well as patients considering specific therapies (e.g., tamoxifen, warfarin) has been suggested.

Associations between drug hypersensitivities and HLA haplotypes suggest a key role for immune mechanisms, especially those leading to skin involvement. Hypersensitivity to the anti-HIV medication abacavir is strongly associated with HLA-B*57:01 (Chap. 202). In Taiwan, within a homogeneous Han Chinese population, a strong association was observed between SJS/TEN (but not DIHS) related to carbamazepine and HLA-B*15:02. In the same population, a strong association was found between HLA-B*58:01 and SJS, TEN, or DIHS related to allopurinol. These associations are drug and phenotype specific; that is, HLA-specific T-cell stimulation by medications leads to distinct reactions. However, while this genetic association is strong, it is not sufficient to cause severe drug hypersensitivity reactions.

GLOBAL CONSIDERATIONS

Recognition of HLA associations with drug hypersensitivity has resulted in recommendations to screen high-risk populations. Genetic screening for HLA-B*57:01 to prevent abacavir hypersensitivity, which carries a 100% negative predictive value when patch test confirmed and 55% positive predictive value generalizable across races, is becoming the clinical standard of care worldwide (number needed to treat = 13). The U.S. Food and Drug Administration has recommended HLA-B*15:02 screening of Asian individuals prior to a new prescription of carbamazepine. The American College of Rheumatology has recommended HLA-B*58:01 screening of Han Chinese patients prescribed allopurinol. To date, screening for a single HLA (but not multiple HLA haplotypes) in specific populations has been determined to be cost-effective (e.g., HLA-B*1301 screening in Chinese patients with leprosy treated with dapsone). Genetic testing for specific HLA haplotypes and functional screening for TCR repertoire to identify patients at risk is becoming more widely available and heralds the era of personalized medicine and pharmacogenomics.

CLINICAL PRESENTATION OF CUTANEOUS DRUG REACTIONS

NONIMMUNE CUTANEOUS REACTIONS

Exacerbation or Induction of Dermatologic Diseases

A variety of drugs can exacerbate preexisting diseases or induce—or unmask—a disease that may or may not disappear after withdrawal of the inducing medication. For example, NSAIDs, lithium, beta blockers, tumor necrosis factor (TNF) antagonists, interferon (IFN) α, and angiotensin-converting enzyme (ACE) inhibitors can exacerbate plaque psoriasis, whereas antimalarials and withdrawal of systemic glucocorticoids can worsen pustular psoriasis. The situation of TNF-α inhibitors is unusual, as this class of medications is used to treat psoriasis; however, they may induce psoriasis (especially palmoplantar) in patients being treated for other conditions. Acne may be induced by glucocorticoids, androgens, lithium, and antidepressants. Follicular papular or pustular eruptions of the face and trunk resembling acne frequently occur with epidermal growth factor receptor (EGFR) antagonists, mitogen-activated protein kinase (MEK) inhibitors, and other targeted inhibitors. With EGFR antagonists, the severity of the eruption correlates with a better anticancer effect. This rash is typically responsive to and prevented by tetracycline antibiotics.

Several medications induce or exacerbate autoimmune disease. Checkpoint inhibitors induce a wide array of systemic autoimmune reactions, including in skin. Interleukin (IL) 2, IFN-α, and anti-TNF-α are associated with new-onset systemic lupus erythematosus (SLE). Drug-induced lupus is classically marked by antinuclear and antihistone antibodies and, in some cases, anti-double-stranded DNA (D-penicillamine, anti-TNF-α) or perinuclear antineutrophil cytoplasmic antibodies (p-ANCA) (minocycline). Subacute cutaneous lupus erythematosus (SCLE) can be induced by a growing list of drugs, including thiazide diuretics, proton pump inhibitors, TNF inhibitors, terbinafine, and minocycline. Drug-induced dermatomyositis may rarely occur with TNF inhibitors or capecitabine; hydroxyurea can induce skin findings of dermatomyositis. IFN and TNF inhibitors, as well as checkpoint inhibitors, can induce granulomatous disease and sarcoidosis. Autoimmune blistering diseases may be drug induced as well: pemphigus by D-penicillamine and ACE inhibitors; bullous pemphigoid by DPP4 inhibitors, furosemide, and PD-1 inhibitors; and linear IgA bullous dermatosis by vancomycin. Other medications may cause highly specific cutaneous reactions. Gadolinium contrast has been associated with nephrogenic systemic fibrosis, a condition of sclerosing skin with rare internal organ involvement; advanced renal compromise may be an important risk factor. Granulocyte colony-stimulating factor, azacitidine, all-trans-retinoic acid, the FLT3 inhibitor class of drugs, and rarely levamisole-contaminated cocaine may induce neutrophilic dermatoses. In this setting, the hypothesis that a drug may be responsible should always be considered, even after the treatment is complete. In addition, reactions may develop in cases of long-term medication therapy due to changes in dosing or host metabolism. Resolution of the cutaneous reaction may be delayed upon discontinuation of the medication.

Photosensitivity Eruptions

Photosensitivity eruptions are usually most marked in sun-exposed areas, but they may extend to sun-protected areas. The mechanism is almost always phototoxicity. Phototoxic reactions resemble sunburn and can occur with first exposure to a drug. Blistering may occur in drug-related pseudoporphyria, most commonly with NSAIDs. The severity of the reaction depends on the tissue level of the drug, its efficiency as a photosensitizer, and the extent of exposure to the activating wavelengths of ultraviolet (UV) light (Chap. 61).

Common orally administered photosensitizing drugs include fluoroquinolones, tetracycline antibiotics, and trimethoprim/sulfamethoxazole. Other drugs less frequently implicated are chlorpromazine, thiazides, NSAIDs, and BRAF inhibitors. Voriconazole may result in severe photosensitivity, accelerated photoaging, and cutaneous carcinogenesis.

Because UV-A and visible light, which trigger these reactions, are not easily absorbed by nonopaque sunscreens and are transmitted through window glass, photosensitivity reactions may be difficult to block. Photosensitivity reactions abate with removal of either the drug or UV radiation, use of sunscreens that block UV-A light, and treatment of the reaction as one would a sunburn. Rarely, individuals develop persistent reactivity to light, necessitating long-term avoidance of sun exposure. Some chemotherapeutic agents, such as methotrexate, can induce a UV-recall reaction characterized by an erythematous, slightly scaly eruption at sites of prior severe sun exposure.

Pigmentation Changes

Drugs, either systemic or topical, may cause a variety of pigmentary changes in the skin by triggering melanocyte production of melanin (as in the case of oral contraceptives causing melasma) or due to deposition of drug or drug metabolites. Long-term minocycline and amiodarone may cause blue-gray pigmentation. Phenothiazine, gold, and bismuth result in gray-brown pigmentation of sun-exposed areas. Numerous cancer chemotherapeutic agents may be associated with characteristic patterns of pigmentation (e.g., bleomycin, busulfan, daunorubicin, cyclophosphamide, hydroxyurea, fluorouracil, and methotrexate). Clofazimine causes a drug-induced lipofuscinosis with characteristic red-brown coloration. Hyperpigmentation of the face, mucous membranes, and pretibial and subungual areas occurs with antimalarials. Quinacrine causes generalized yellow discoloration. Pigmentation changes may also occur in mucous membranes (busulfan, bismuth), conjunctiva (chlorpromazine, thioridazine, imipramine, clomipramine), nails (zidovudine, doxorubicin, cyclophosphamide, bleomycin, fluorouracil, hydroxyurea), hair, and teeth (tetracyclines).

Warfarin Necrosis of Skin

This rare reaction (0.01–0.1%) usually occurs between the third and tenth days of therapy with warfarin, usually in women. Common sites are breasts, thighs, and buttocks (Fig. 60-1). Lesions are sharply demarcated, erythematous, or purpuric, and may progress to form large, hemorrhagic bullae with necrosis and eschar formation.

Warfarin anticoagulation in protein C or S deficiency causes an additional reduction in already low circulating levels of endogenous anticoagulants, permitting hypercoagulability and thrombosis in the cutaneous microvasculature, with consequent areas of necrosis. Heparin-induced necrosis may have clinically similar features but is probably due to heparin-induced platelet aggregation with subsequent occlusion of blood vessels; it can affect areas adjacent to the injection site or more distant sites if infused. Levamisole-tainted cocaine (and more recently, heroin) can induce similar skin necrosis; however, the distribution tends to involve the ears and cheeks predominantly, with stellate or retiform purpura. Patients may have abnormal white blood cell counts and may be dual P- and C-ANCA positive.

Drug-Induced Hair Disorders

DRUG-INDUCED HAIR LOSS

Medications may affect hair follicles at two different phases of their growth cycle: anagen (growth) or telogen (resting). Anagen effluvium occurs within days of drug administration, especially with antimetabolite or other chemotherapeutic drugs. In contrast, in telogen effluvium, the delay is 2–4 months following initiation of a new medication. Both present as diffuse, nonscarring alopecia most often reversible after discontinuation of the responsible agent.

A considerable number of drugs have been associated with hair loss. These include antineoplastic agents (alkylating agents, bleomycin, vinca alkaloids, platinum compounds), anticonvulsants (carbamazepine, valproate), beta blockers, antidepressants, antithyroid drugs, IFNs, oral contraceptives, and cholesterol-lowering agents.

DRUG-INDUCED HAIR GROWTH

Medications may also cause hair growth. Hirsutism is an excessive growth of terminal hair with masculine hair growth pattern in a female, most often on the face and trunk, due to androgenic stimulation of hormone-sensitive hair follicles (anabolic steroids, oral contraceptives, testosterone, corticotropin). Hypertrichosis is a distinct pattern of hair growth, not in a masculine pattern, typically located on the forehead and temporal regions of the face. Drugs responsible for hypertrichosis include anti-inflammatory drugs, glucocorticoids, vasodilators (diazoxide, minoxidil), diuretics (acetazolamide), anticonvulsants (phenytoin), immunosuppressive agents (cyclosporine A), psoralens, and zidovudine.

Changes in hair color or structure are uncommon adverse effects from medications. Hair discoloration may occur with chloroquine, IFN-α, chemotherapeutic agents, and tyrosine kinase inhibitors. Changes in hair structure have been observed in patients given EGFR inhibitors, BRAF inhibitors, tyrosine kinase inhibitors, and acitretin.

Drug-Induced Nail Disorders

Drug-related nail disorders usually involve all 20 nails and need months to resolve after withdrawal of the medication. The pathogenesis is most often toxic. Drug-induced nail changes include Beau’s line (transverse depression of the nail plate), onycholysis (detachment of the distal part of the nail plate), onychomadesis (detachment of the proximal part of the nail plate), pigmentation, and paronychia (inflammation of periungual skin).

ONYCHOLYSIS

Onycholysis occurs with tetracyclines, fluoroquinolones, retinoids, NSAIDs, and others, including many chemotherapeutic agents, and may be triggered by exposure to sunlight.

ONYCHOMADESIS

Onychomadesis is caused by temporary arrest of nail matrix mitotic activity. Common drugs reported to induce onychomadesis include carbamazepine, lithium, retinoids, and chemotherapeutic agents such as taxanes.

PARONYCHIA

Paronychia and multiple pyogenic granulomas with progressive and painful periungual abscess of fingers and toes are side effects of systemic retinoids, lamivudine, indinavir, and anti-EGFR monoclonal antibodies.

NAIL DISCOLORATION

Some drugs—including anthracyclines, taxanes, fluorouracil, psoralens, and zidovudine—may induce nail bed hyperpigmentation through melanocyte stimulation. It appears to be reversible and dose dependent.

Toxic Erythema of Chemotherapy and Other Chemotherapy Reactions

Because many agents used in cancer chemotherapy inhibit cell division, rapidly proliferating elements of the skin, including hair, mucous membranes, and appendages, are sensitive to their effects. A broad spectrum of chemotherapy-related skin toxicities has been reported, including neutrophilic eccrine hidradenitis, sterile cellulitis, exfoliative dermatitis, and flexural erythema; recent nomenclature classifies these under the unifying diagnosis of toxic erythema of chemotherapy (TEC) (Fig. 60-2). Acral erythema is marked by dysesthesia and an erythematous, edematous eruption of the palms and soles. Common causes include cytarabine, doxorubicin, methotrexate, hydroxyurea, fluorouracil, and capecitabine.

The recent introduction of many new monoclonal antibody and small molecular signaling inhibitors for the treatment of cancer has been accompanied by numerous reports of skin and hair toxicity; only the most common of these are mentioned here. EGFR antagonists induce follicular eruptions and nail toxicity after a mean interval of 10 days in a majority of patients. Xerosis, eczematous eruptions, acneiform eruptions, and pruritus are common. Erlotinib is associated with marked hair textural changes. Sorafenib, a tyrosine kinase inhibitor, may result in follicular eruptions and focal bullous eruptions at palmoplantar, flexural sites or areas of frictional pressure. BRAF inhibitors are associated with photosensitivity, palmoplantar hyperkeratosis, hair curling, dyskeratotic (Grover’s-like) rash, hyperkeratotic benign cutaneous neoplasms, and keratoacanthoma-like squamous cell carcinomas. Rash, pruritus, and vitiliginous depigmentation have been reported in association with ipilimumab (anti-CTLA4) treatment. Up to 50% of patients experience immune-mediated skin eruptions, including granulomatous reactions, dermatomyositis, panniculitis, and vasculitis. The checkpoint inhibitor class of drugs (including anti-CTLA4, anti-PD-1, and anti-PD-L1 agents) can induce a wide range of cutaneous eruptions beyond vitiligo, including lichenoid, eczematous, granulomatous, papulosquamous, and panniculitis eruptions.

IMMUNE CUTANEOUS REACTIONS: COMMON

Maculopapular Eruptions

Morbilliform or maculopapular eruptions (Fig. 60-3) are the most common of all drug-induced reactions, often start on the trunk or intertriginous areas, and consist of blanching erythematous macules and papules that are symmetric and confluent. Nonblanching, dusky, or bright-red macules as well as mucosal involvement should raise concern for a more severe reaction. Facial involvement in morbilliform eruptions is also uncommon, and the presence of extensive facial lesions with facial edema suggests DIHS. Diagnosis of morbilliform eruptions is rarely assisted by laboratory testing or skin biopsy.

Morbilliform eruptions may be associated with moderate to severe pruritus and fever. A viral exanthem is another differential diagnostic consideration, especially in children, and graft-versus-host disease is also a consideration in the proper clinical setting. Absence of enanthems; absence of ear, nose, throat, and upper respiratory tract symptoms; and polymorphism of the skin lesions support a drug rather than a viral eruption. Common offenders include aminopenicillins, cephalosporins, antibacterial sulfonamides, allopurinol, and antiepileptic drugs. Beta blockers, calcium channel blockers, and ACE inhibitors are rarely the culprit; however, any drug can cause a morbilliform exanthem. Certain medications carry very high rates of morbilliform eruption, including nevirapine and lamotrigine, even in the absence of DIHS reactions. Lamotrigine morbilliform rash is associated with higher starting doses, rapid dose escalation, concomitant use of valproate (which increases lamotrigine levels and half-life), and use in children.

Maculopapular reactions usually develop within 1 week of initiation of therapy and last less than 2 weeks. Occasionally, these eruptions resolve despite continued use of the responsible drug. Because the eruption may also worsen, the suspect drug should be discontinued unless it is essential. It is important to note that the rash may continue to progress for a few days up to 1 week following medication discontinuation. Oral antihistamines and emollients may help relieve pruritus. Short courses of potent topical glucocorticoids can reduce inflammation and symptoms. Systemic glucocorticoid treatment is rarely indicated.

Pruritus

Pruritus is associated with almost all drug eruptions and, in some cases, may represent the only symptom of the adverse cutaneous reaction. It may be alleviated by antihistamines such as hydroxyzine or diphenhydramine. Pruritus stemming from specific medications may require distinct treatment, such as selective opiate antagonists for opiate-related pruritus.

Urticaria/Angioedema/Anaphylaxis

Urticaria, the second most frequent type of cutaneous reaction to drugs, is characterized by pruritic, red wheals of varying size rarely lasting more than 24 hours. It has been observed in association with nearly all drugs, most frequently ACE inhibitors, aspirin, NSAIDs, penicillin, and blood products. However, medications account for no more than 10–20% of acute urticaria cases. Deep edema within dermal and subcutaneous tissues is known as angioedema and may involve respiratory and gastrointestinal mucous membranes. Urticaria and angioedema may be part of a life-threatening anaphylactic reaction.

Drug-induced urticaria may be caused by three mechanisms: an IgE-dependent mechanism, circulating immune complexes (serum sickness), and nonimmunologic activation of effector pathways. IgE-dependent urticarial reactions usually occur within 36 hours of drug exposure but can occur within minutes. Immune complex–induced urticaria associated with serum sickness reactions usually occurs 6–12 days after first exposure. In this syndrome, the urticarial eruption (typically polycyclic plaques over distal joints) may be accompanied by fever, hematuria, arthralgias, hepatic dysfunction, and neurologic symptoms. Certain drugs, such as NSAIDs, ACE inhibitors, angiotensin II antagonists, radiographic dye, and opiates, may induce urticarial reactions, angioedema, and anaphylaxis in the absence of drug-specific antibodies through direct mast-cell degranulation.

Radiocontrast agents are a common cause of urticaria and, in rare cases, can cause anaphylaxis. High-osmolality radiocontrast media are about five times more likely to induce urticaria (1%) or anaphylaxis than are newer low-osmolality media. About one-third of those with mild reactions to previous exposure react on reexposure. Pretreatment with prednisone and diphenhydramine reduces reaction rates.

The treatment of urticaria or angioedema depends on the severity of the reaction. In severe cases with respiratory or cardiovascular compromise, epinephrine and intravenous glucocorticoids are the mainstay of therapy. For patients with urticaria without symptoms of angioedema or anaphylaxis, drug withdrawal and oral antihistamines are usually sufficient. Future drug avoidance is recommended; rechallenge, especially in individuals with severe reactions, should only occur in an intensive care setting.

Anaphylactoid Reactions

Vancomycin is associated with red man syndrome, a histamine-related anaphylactoid reaction characterized by flushing, diffuse maculopapular eruption, and hypotension. In rare cases, cardiac arrest may be associated with rapid intravenous (IV) infusion of the medication.

Irritant/Allergic Contact Dermatitis

Patients using topical medications may develop an irritant or allergic contact dermatitis to the medication itself or to a preservative or other component of the formulation. Reactions to neomycin sulfate, bacitracin, and polymyxin B are common. Contact dermatitis may be seen to adhesive tapes, leading to irritation or blisters around ports and IV sites (Fig. 60-4). Harsh disinfectant skin cleansers may lead to localized irritant dermatitis.

Fixed Drug Eruptions

These less common reactions are characterized by one or more sharply demarcated, dull red to brown lesions, sometimes with central dusky violaceous erythema and central bulla (Fig. 60-5). Hyperpigmentation often results after resolution of the acute inflammation. With rechallenge, the process recurs in the same (fixed) location but may spread to new areas as well. Lesions often involve the lips, hands, legs, face, genitalia, and oral mucosa, and cause a burning sensation. Most patients have multiple lesions. Fixed drug eruptions have been associated with pseudoephedrine (frequently a nonpigmenting reaction), phenolphthalein (in laxatives), sulfonamides, tetracyclines, NSAIDs, barbiturates, and others.

IMMUNE CUTANEOUS REACTIONS: RARE AND SEVERE

Drug-Induced Hypersensitivity Syndrome

DIHS is a systemic drug reaction also known as DRESS (drug reaction with eosinophilia and systemic symptoms) syndrome; because eosinophilia is not always present, the term DIHS is preferred. Clinically, DIHS presents with a prodrome of fever and flu-like symptoms for several days, followed by the appearance of a diffuse morbilliform eruption, usually involving the face (Fig. 60-6). Facial swelling and hand/foot swelling are often present. Systemic manifestations include lymphadenopathy, fever, and leukocytosis (often with eosinophilia or atypical lymphocytosis), as well as hepatitis, nephritis, pneumonitis, myositis, and gastroenteritis, in descending order. Distinct patterns of timing of onset and organ involvement may exist. For example, allopurinol classically induces DIHS with renal involvement; cardiac and lung involvement are more common with minocycline; gastrointestinal involvement is almost exclusively seen with abacavir; and some medications typically do not induce eosinophilia (abacavir, dapsone, lamotrigine). The cutaneous reaction usually begins 2–8 weeks after the drug is started and persists after drug cessation. Signs and symptoms may continue for several weeks, especially those associated with hepatitis. The eruption recurs with rechallenge, and cross-reactions among aromatic anticonvulsants, including phenytoin, carbamazepine, and phenobarbital, are common. Other drugs causing DIHS include antibacterial sulfonamides and other antibiotics. Hypersensitivity to reactive drug metabolites, hydroxylamine for sulfamethoxazole and arene oxide for aromatic anticonvulsants, may be involved in the pathogenesis of DIHS. Recent research suggests that inciting drugs may reactivate quiescent human herpes viruses, including herpesviruses 6 and 7, EBV, and cytomegalovirus (CMV), resulting in expansion of viral-specific CD8+ T lymphocytes and subsequent end-organ damage. Viral reactivation may be associated with a worse clinical prognosis. Mortality rates as high as 10% have been reported, with most fatalities resulting from liver failure. Systemic glucocorticoids (1.5–2 mg/kg/d prednisone equivalent) should be started and tapered slowly over 8–12 weeks, during which time clinical symptoms and labs (including complete blood count with differential, basic metabolic panel, and liver function tests) should be followed carefully. A steroid-sparing agent such as mycophenolate mofetil, IV immunoglobulin, or cyclosporine may be indicated in cases of rapid recurrence upon steroid taper. In all cases, immediate withdrawal of the suspected culprit drug is required. Given the severe long-term complications of myocarditis, patients should undergo cardiac evaluation in cases of severe DIHS or if heart involvement is suspected due to hypotension or arrhythmia. Patients should be closely monitored for resolution of organ dysfunction and for development of late-onset autoimmune thyroiditis and diabetes (up to 6 months).