Chapter 30. Commonly Encountered Genital Dermatoses

Patients may seek a sexually transmitted disease (STD) evaluation for essentially anything they perceive as abnormal and that is located “below the belt.” Although the presence of an STD should always be considered and ruled out, many patients who seek care for a suspected STD have nonsexually transmitted genital conditions. For this reason, clinicians should have a basic understanding of the spectrum of both normal skin findings and common dermatologic conditions that arise in the genitalia so they can prescribe appropriate therapy, refer the patient to a dermatologist for additional evaluation and management when necessary, or provide reassurance.

This chapter discusses the nonsexually transmitted dermatologic conditions most commonly encountered in the STD clinic setting, as well as normal variants. The discussion of pathologic lesions that follows is organized by morphology and color of lesion. A review of definitions employed to describe skin lesions is found in Table 30–1. A section on ectoparasites concludes the chapter. For a more comprehensive review of genital dermatology, the reader is referred to the text references listed below.

A thorough history is an essential component in the evaluation of an individual presenting with genital lesions or rash. Useful questions to ask include the following:

• (1) How long has the lesion or rash been present? The duration of a genital lesion is important for directing evaluation. For example, a genital ulcer or atypical lesion that has been slowly growing over the course of months to years implies the need for immediate biopsy, whereas an ulcer of shorter duration (that does not appear atypical) may warrant a workup for common infectious etiologies, and perhaps empiric therapy, with biopsy reserved for situations in which the workup is negative and the lesion fails to resolve.
• (2) Does the lesion look the same now as it did when it first appeared? If not, how is it different? Understanding the evolution of a lesion or rash may assist the clinician in narrowing the differential diagnosis. For example, a patient may have self-treated a herpes simplex virus infection, resulting in a contact dermatitis. Only a thorough history will allow the clinician to sift through the details and put the story together.
• (3) What other areas are involved? Are the abnormalities confined to the genital region or widespread? In general, disseminated rashes require more urgent evaluation than localized rashes, particularly if accompanied by systemic signs and symptoms. In addition, syphilis should always be considered in the evaluation of a disseminated rash (see Chapter 19).
• (4) What are the characteristics of the rash or lesion? Was the onset of the rash or lesion associated with anything in particular? A pruritic rash may imply an ectoparasitic infection or a drug reaction, whereas a genital rash that stings and burns may be a result of contact dermatitis. In the case of irritant contact dermatitis, the patient may recall the close temporal relationship between application of an offending product and symptom onset.
• (5) Has this ever happened to you before? If so, what was determined to be the cause that time? Fixed drug eruption, a lesion that occurs at the same anatomic site (and worsens) with each exposure to the drug, would often escape diagnosis unless the clinician elicited a previous history. Likewise, a patient with a widespread dermatosis, such as psoriasis, may have experienced genital lesions in the past.
• (6) What are your hygiene habits? What products does your partner use? Do you use condoms, lubricants, or spermicides when you have sex? It is often helpful to address issues of personal hygiene and sexual practice in an open-ended fashion, followed by more pointed questions. At times it may be necessary to ask patients to review their daily hygiene routine with the clinician as this may jog their memories.

Normal Anatomic Variants: Introduction

When a patient presents for initial evaluation of a genital condition, one of the first issues to consider is whether or not the abnormality in question is pathologic or simply a normal variant. This distinction is important, because intervention involving a normal anatomic variant often is not in the best interest of the patient. Among the commonly encountered normal variants are pearly penile papules, vestibular papillae, and Fordyce spots.

Pearly Penile Papules

Essentials of Diagnosis

• • Skin-colored papules most commonly located in the coronal sulcus of the penis.
• • Asymptomatic papules with rounded tips and discrete bases.

One of the most commonly encountered dermatologic conditions in male patients who seek care at STD clinics, pearly penile papules are usually brought to the attention of the clinician when the patient presents for evaluation of possible condylomata acuminata. The papules are found more commonly in uncircumcised men and are located primarily around the coronal sulcus. They may also be found on the distal penile shaft, near the frenulum, or on the posterior part of the glans penis. These asymptomatic lesions are usually flesh-colored or pink and rounded with discrete bases. They may be elongated into papillae (see Figure 30–1).

The primary entity with which pearly penile papules are confused is condylomata acuminata. Unlike pearly penile papules, however, condylomata acuminata often have spiked tips or are contiguous at the base.

The diagnosis of pearly penile papules is based on the clinical appearance. Biopsy is usually not necessary but, if performed, would reveal a benign angiofibroma. Reassurance is the only treatment necessary.

Vestibular Papillae

Essentials of Diagnosis

• • Asymptomatic, small, monomorphous, symmetric tubular papillae located within the vaginal vestibule.
• • Often confused with condylomata acuminata.

Vestibular papillae occur in one third to one half of women and are a normal anatomic variant distinguished by monomorphic appearance, rounded tips, discrete nature of the base of the lesions, and symmetric distribution. Some variants of vestibular papillae are short and confluent, giving a cobblestone texture to the skin. These lesions are typically found in the vaginal vestibule and are asymptomatic. Although there is some debate as to the role of human papillomavirus (HPV) in the development of vestibular papillae, the current consensus is that HPV is not related to these lesions.

The primary entity with which vestibular papillae are confused is condylomata acuminata. The two conditions can usually be distinguished from one another based on the appearance of the lesions.

The diagnosis of vestibular papillae is based on the appearance and distribution of the lesions. Application of acetic acid 5% does not reliably distinguish these lesions from genital warts. Other than reassuring the patient, no treatment is necessary.

Fordyce Spots

Essentials of Diagnosis

• • Flesh-colored to yellowish, small, smooth papules.
• • Most commonly located on the medial aspect of the labia minora or the proximal quarter of the penile shaft.

Fordyce spots are enlarged sebaceous glands located on modified mucous membranes that typically involve the medial aspect of the labia minora in women and the proximal quarter of the penile shaft in men. They are asymptomatic, papular, and flesh-colored to yellow in appearance (see Figure 30–2). They may be discrete and multilobular or confluent.

No laboratory studies are necessary; diagnosis is based on clinical appearance. Although the appearance of Fordyce spots is characteristic, it may be possible to confuse them with small condylomata acuminata. No treatment is necessary.

Flesh-Colored Papules

Molluscum Contagiosum

Essentials of Diagnosis

• • Common viral infection characterized by flesh-colored, pearly papules with central umbilication.
• • Self-limited in immunocompetent hosts.

General Considerations

Molluscum contagiosum is caused by the molluscum contagiosum virus, a member of the DNA poxvirus group, and is common in children and young adults. It is usually transmitted through sexual and other close contact.

Clinical Findings

The infection is characterized by firm, dome-shaped, flesh-colored, “pearly” papules with central umbilication (see Figure 30–3). Although the classic central umbilication may not be present on all lesions, usually there are several on which this depression may be found. If the lesion of molluscum contagiosum is incised, a central core, usually waxy, can be expressed. The central umbilication and waxy core help differentiate molluscum contagiosum from other diseases. Lesions are most often asymptomatic but may be described as pruritic. They are most often located in the pubic area, proximal and medial thighs, and penile shaft. Lesions are larger and more numerous in immunosuppressed patients.

Biopsy is rarely required to diagnose molluscum contagiosum. If performed, histologic examination will reveal large eosinophilic inclusion bodies within epidermal cells.

Differential Diagnosis

Molluscum contagiosum may be confused with condylomata acuminata, and molluscum lesions that are more vesicular in appearance may be confused with herpes simplex virus. Sebaceous gland hyperplasia, basal cell carcinoma, and, in immunosuppressed individuals, fungal infections such as cryptococcosis and histoplasmosis should also be considered. If the patient presents with molluscum-like lesions in the setting of systemic symptoms, evaluation should proceed quickly to rule out disseminated fungal infection.

Treatment

Although the course of infection in the immunocompetent host is usually self-limited, generally resolving over months, patients may desire treatment for cosmetic purposes. In contrast, molluscum contagiosum in the immunocompromised host is often persistent, larger, and more distressing to the patient in terms of appearance and often requires treatment.

Treatment requires either destructive or immunomodulatory modalities. Molluscum contagiosum can be effectively treated with curettage or incision followed by expression of the central white core of the lesion, also known as the “molluscum body.” Other therapeutic modalities include electrosurgery and cryotherapy. Cantharidin may be used for lesions found outside the genital region but, because of painful blisters and erythema that result from therapy, should be avoided in sensitive areas of the body. Recent studies have found variable success with imiquimod, applied three times a week overnight for up to 16 weeks; clearance rates have ranged from 33% to 100%, depending on the population studied. Finally, podophyllin, podofilox 0.5%, laser therapy, and trichloroacetic acid may be used.

Molluscum contagiosum is usually not eliminated in one treatment and lesions may continue to occur for a time after treatment. Relapse is particularly frequent in immunocompromised hosts.

Squamous Intraepithelial Neoplasia & Squamous Cell Carcinoma

Essentials of Diagnosis

• • Lesions are characterized by skin-colored, pink or white, flat-topped papules or plaques that may ulcerate over time.
• • Lesions typically are present for a year or longer.

General Considerations

The terminology describing squamous intraepithelial neoplasia has proved to be confusing at times to the nondermatologist. The histology of intraepithelial neoplasia is described using terminology similar to that used to describe Papanicolaou (Pap) smears and represents a spectrum from mild dysplasia of the epithelium to severe dysplasia (carcinoma in situ). The final step in this pathway is frankly invasive squamous cell carcinoma, which has metastatic capability. Vulvar involvement with intraepithelial neoplasia is referred to as vulvar intraepithelial neoplasia, and penile involvement as penile intraepithelial neoplasia. There is currently a move to use this more general terminology and steer away from the terms used to describe various types of intraepithelial neoplasia that were used in the past that included, but were not limited to, Bowen’s disease, bowenoid papulosis, keratotic balanitis, and erythroplasia of Queyrat.

Multifocal intraepithelial neoplasia has been documented to occur in a slightly younger age group (20–40 years) than unifocal disease (typically >50 years) and is more likely to be linked to high-risk HPV types, primarily 16 and 18. Multifocal intraepithelial neoplasia is less likely to progress to frankly invasive squamous cell carcinoma, as compared with single lesion intraepithelial neoplasia.

Risk factors for the development of intraepithelial neoplasia include advanced age, smoking, and compromised immune status. The presence of a long-standing inflammatory dermatologic condition such as lichen sclerosis is a risk factor for the development of squamous cell carcinoma.

Clinical Findings

The appearance of intraepithelial neoplasia is variable, and lesions may be flesh-colored, red, or white. Multifocal intraepithelial neoplasia (formerly known as bowenoid papulosis) usually appears as multiple discrete flat-topped papules or plaques on the glans, prepuce, and penile shaft in men or the vestibule and outer labia minora in women. Single lesion intraepithelial neoplasia is usually a larger, well-defined patch or plaque with scale that may ulcerate over time. Some forms of intraepithelial neoplasia, especially after progression to squamous cell carcinoma, may appear more verrucous, become friable, and bleed easily (see Figure 30–4). Long-standing squamous cell carcinoma may result in destruction of the genitalia (see Figure 30–5).

The history is the key to the correct evaluation and diagnosis of patients with intraepithelial neoplasia and squamous cell carcinoma. The time course of the lesion is long, often on order of years. The lesions are usually asymptomatic, although some patients may complain of pruritus, with growth so slow as to often be imperceptible.

The diagnosis of intraepithelial neoplasia and squamous cell carcinoma should be confirmed by biopsy.

Differential Diagnosis

Vulvar intraepithelial neoplasia and penile intraepithelial neoplasia may be confused with condylomata acuminata. Some forms of squamous cell carcinoma may be confused with granuloma inguinale (donovanosis). Biopsy can distinguish between these etiologies.

Treatment

Treatment of vulvar intraepithelial neoplasia, penile intraepithelial neoplasia, and squamous cell carcinoma involves local destruction or removal of lesions. Patients should be referred to a dermatologist and may require referral to a gynecologist or urologist if the disease process is advanced.

Inflammatory Papules & Plaques

Pityriasis Rosea

Essentials of Diagnosis

• • Characterized by often widespread papulosquamous, hyperpigmented, scaling lesions that develop a “Christmas tree” pattern on the back.
• • Widespread rash is often preceded by a “herald lesion.”

General Considerations

A common rash affecting children and young adults, pityriasis rosea is often asymptomatic but distressing due to its generalized nature. The etiology is unclear but is thought to be a postviral exanthema, a hypothesis supported by the self-limited nature of the rash and the fact that cases often appear in clusters.

Clinical Findings

The first symptoms of pityriasis rosea frequently include nonspecific viral respiratory tract symptoms followed by the development of the herald patch, usually located on the trunk. The herald patch is usually 2–10 cm in diameter, ovoid, erythematous, and slightly raised with a collarette of scale at the margin.

Several days to weeks after the appearance of the herald patch, a widespread rash appears, with lesions typically concentrated on the trunk. The extremities may become involved and, rarely, the palms and soles. Genital involvement may also occur, leading the patient to present to an STD clinician for care. The generalized rash is salmon-colored and, like the herald patch, ovoid with a collarette of scale (see Figure 30–6). Lesions follow Langer lines (cleavage lines) and, when they occur on the back, result in a “Christmas tree” pattern. Pityriasis rosea may occur in an inverse form, in which the rash is concentrated on the extremities and the trunk is spared. The rash also may be localized.

Although classic pityriasis rosea is readily recognized, less typical patterns of rash distributions often present diagnostic challenges. The most common symptom reported in patients with pityriasis is pruritus. Otherwise, no systemic symptoms occur at the time the rash is present.

The diagnosis of pityriasis rosea is usually based on the clinical appearance of the rash. Biopsy is rarely necessary to make the diagnosis.

Differential Diagnosis

The herald lesion may be confused with tinea corporis, especially in the absence of the generalized rash. Secondary syphilis is an important consideration in the differential diagnosis, and a nontreponemal serologic test (eg, rapid plasma reagin [RPR] or Venereal Disease Research Laboratories [VDRL]) should be performed to rule out this etiology in sexually active individuals. (See Chapter 19 for discussion of the presentation of secondary syphilis.)

Treatment

The rash usually lasts 5–8 weeks, and the control of pruritus is the primary goal of therapy. Topical or systemic corticosteroids and a commonly used antihistamine such as hydroxyzine, 25 mg orally up to four times daily, may be used to provide symptom relief.

Tinea Cruris

Essentials of Diagnosis

• • Superficial dermatophyte infection most commonly caused by Trichophyton rubrum, Trichophyton mentagrophytes, and Microsporum canis.
• • Rash often has a leading edge and scale.

General Considerations

Tinea cruris is a common dermatologic condition encountered by primary care providers and STD clinicians. The condition is most commonly caused by the dermatophytes T rubrum, T mentagrophytes, and M canis and is transmitted by transfer of arthroconidia-laden scales through direct contact with an infected individual or through contact with objects that carry the infected scales. Autoinfection may also play a role.

Clinical Findings

Once infection occurs, the organism invades the stratum corneum and the terminal hair of the affected area, resulting in a rash that frequently extends from the groin to the inner thighs and perineal or perianal areas. The rash often has a leading edge and scale with central clearing, giving it an annular appearance. The primary symptom is pruritus.

The diagnosis may be confirmed by scraping the leading edge of the affected skin and adding 10–15% potassium hydroxide to the specimen. Examination under a microscope often reveals septate hyphae coursing through the squamous cells. A culture of skin scrapings, plated on Sabouraud agar media and incubated at room temperature, typically yields an organism within 2 weeks.

Differential Diagnosis

Seborrheic dermatitis, psoriasis, candidiasis, eczema, and lichen simplex chronicus are the primary dermatoses to be differentiated from tinea cruris. Eczema, unlike tinea cruris, more commonly involves the labia majora and scrotum. Psoriasis can usually be differentiated based on the presence of typical psoriatic lesions elsewhere on the body.

Treatment

Treatment of tinea cruris most often involves topical therapy with an antifungal agent such as an azole (miconazole, clotrimazole, etc), an allylamine (naftifine, terbinafine), benzylamine derivatives (butenafine), and hydroxypyridones (ciclopirox olamine). Occasionally, oral therapy may be required. Possible oral therapeutic agents include fluconazole, 150–300 mg weekly for 2–4 weeks; itraconazole, 200 mg/day for 1 week; terbinafine, 250 mg/day for 2–4 weeks; ketoconazole, 200 mg/day for 4–8 weeks; and griseofulvin, 250 mg twice daily until cured.

Contact Dermatitis

Essentials of Diagnosis

• • May be caused by allergic response to an agent or the direct irritant effect of an agent.
• • Acute inflammation manifests as erythema, edema, vesicles, bullae, or superficial erosions with exudation.
• • Chronic inflammation is characterized by lichenification, scaling, fissures, and hypo- or hyperpigmentation.

General Considerations

Contact dermatitis is one of the most common non-STD genital dermatoses encountered in a patient presenting for STD evaluation. It is characterized by an inflammatory response mediated by a specific immunologic response (type IV) to an allergen (allergic contact dermatitis), or occurring as the result of a direct irritant effect of an agent on the skin (irritant contact dermatitis).

Clinical Findings

The inflammatory process may be acute or chronic at the time the patient presents for care. The acute phase of a contact reaction is often characterized by erythema, edema, vesicles, and bullae, with progression to erosions and exudation in some cases (see Figure 30–7). The patient may complain about irritation, itching, and burning at this time. The onset of symptoms may provide a clue to the pathophysiology of the response, because allergic contact dermatitis classically presents within 12–48 hours of antigen exposure and persists for 3–4 weeks, whereas irritant contactants may elicit symptoms within minutes to hours. However, this is not a hard and fast rule, and the differentiation between potential pathophysiologies (allergic versus irritant) involved in the process is not important in terms of determining the treatment regimen.

Although the distribution and location of a contact dermatitis rash can give important clues as to the offending agent when located in other areas of the body, the warmth and dampness that is inherently present in the genital area often lead to the contactant being spread around and the subsequent loss of any defined pattern. If the etiology of the allergic or irritative response is not elicited and the response becomes chronic, the skin often becomes lichenified and scaly, and fissures may develop. In addition, postinflammatory hyper- or hypopigmentation may result, leading to additional cosmetic concerns. Table 30–2 lists some common causes of contact dermatitis affecting the genital region.

The diagnosis of contact dermatitis is dependent on a thorough history and examination of the patient. It is important to ask about sexual and grooming habits of both the patient and his or her sex partners, because the patient’s dermatologic condition may be a manifestation of a response to something the partner is using (ie, condoms or spermicide). Examining the skin outside the genital area may yield important clues as well.

Patients in whom a specific contactant cannot be implicated or who fail to respond to appropriate treatment may require referral to a dermatologist for patch testing. Patch testing is not a useful diagnostic test for irritant contact dermatitis, which is not an immunologically mediated response.

Differential Diagnosis

The differential diagnosis of contact dermatitis is broad. For chronic contact dermatitis it includes atopic dermatitis, seborrheic dermatitis, psoriasis, and fungal infections such as tinea cruris. Acute contact dermatitis may be confused with herpes simplex virus infection, pemphigus vulgaris, candidiasis, and other blistering or erosive diseases. The differentiation between these diseases may be made on the basis of history and the distribution of lesions, especially when other areas of the body are involved.

Treatment

The cornerstone of treatment of contact dermatitis is identification and removal of the offending agent. Unfortunately, the longer the process continues, the more difficult it can be to determine the etiology of the initial insult, especially as patients often self-treat and thereby may confuse the picture. If the specific contactant cannot be identified, the patient should be instructed to avoid all topical agents in the genital area except clear water and petrolatum. Unscented, mild soaps may be used in moderation if the patient feels the need to cleanse the area with something besides water.

Acute contact dermatitis may be improved through the use of cool soaks and sitz baths. Oral prednisone may speed recovery of acute allergic dermatitis at doses of 40–60 mg/day and should be tapered rapidly over 5–10 days. Topical low- and mid-potency corticosteroids, such as 1% hydrocortisone ointment twice daily or triamcinolone 0.1% twice daily, respectively, may be used as well, especially if inflammation is not severe. Topical corticosteroid creams and ointments may be used for chronic contact dermatitis, although long-term use of these products may lead to steroid atrophy. Finally, nighttime sedation (eg, with an antihistamine) should be employed to prevent symptoms of irritation and itching that are often noticed more at night.

Psoriasis

Essentials of Diagnosis

• • Common dermatologic condition that frequently affects the genitalia.
• • Skin findings outside the genital region are often the key to the diagnosis.

General Considerations

Psoriasis is a relatively common dermatologic disorder caused by an unusually rapid proliferation of the epidermis. Although the cause is unknown, there is a strong hereditary component to the disease, and approximately one third of patients report a family history. Psoriasis also is seen more frequently in HIV-infected individuals. For example, preexisting psoriasis may worsen in an individual who becomes HIV-infected or, conversely, an HIV-infected individual with a genetic predisposition may present with psoriasis for the first time. Therefore, psoriasis may be one of the first signs of HIV infection and should lead the clinician to consider HIV testing of the individual, especially when the onset of disease is rapid and the case is severe.

Clinical Findings

Psoriasis is classically manifested as red, sharply demarcated plaques with silvery scale and frequently involves the scalp, elbows, knees, gluteal cleft, and umbilicus. Approximately 50% of patients with psoriasis have typical nail findings including, but not limited, to nail pitting. Genital lesions, when present, are often not as thick as those found on other areas of the body and typically have less scale. Pruritus may or may not be present.

Inverse psoriasis, a variant with prominent genital involvement, may predominantly involve the skinfolds such as the axilla, gluteal fold, inframammary skin, umbilicus, and crural creases. The lesions of inverse psoriasis may not be as thick and well marginated, and the classic silvery scale is often less apparent. Although inverse psoriasis may be seen in immunocompetent hosts, immunodeficient individuals, particularly those who are HIV-infected, are more likely to present with this form of psoriasis.

Psoriasis often has nail manifestations, including nail pitting, “oil-drop spots” (brownish-red discoloration of the nail bed), and onycholysis. Nail findings should be sought during the clinical evaluation of the patient, because they may provide helpful diagnostic clues, especially given the often less characteristic qualities of the genital rash.

The diagnosis is often made on the basis of a consistent genital rash in the setting of characteristic lesions present elsewhere on the body. Biopsy may be necessary to confirm the diagnosis in the absence of extragenital involvement or when the genital lesions are not characteristic.

Differential Diagnosis

The differential diagnosis of genital psoriasis includes lichen simplex chronicus, vulvar intraepithelial neoplasia or penile intraepithelial neoplasia, tinea cruris, and seborrheic dermatitis. Inverse psoriasis, in particular, may be confused with a fungal infection and should be considered in the differential diagnosis when a patient has a refractory yeast infection.

Treatment

A full discussion of the treatment of psoriasis is outside the scope of this chapter. Although topical corticosteroids are first-line therapy, potent and ultrapotent formulations usually are necessary, and long-term corticosteroid use is likely. Patients should be referred to a dermatologist for management.

Lichen Planus

Essentials of Diagnosis

• • Disease of cell-mediated immunity characterized by many different morphologic appearances.
• • Lesion characteristics depend on the type of epithelium involved.

Clinical Findings

Lichen planus is a disease of cell-mediated immunity characterized by well-circumscribed violaceous or brown flat-topped papules with white striae (Wickham striae) and scale, when keratinized epithelium is involved. The glans penis or keratinized surfaces of the vulva may be involved, and lesions may have a polyhedral or an annular configuration. Mucous membrane involvement with lichen planus is marked by the presence of a fernlike or lacy reticular pattern on the vulvar vestibule, vagina, or, in instances when the mouth is involved, the buccal mucosa. Severe mucous membrane involvement, known as erosive lichen planus, may result in denudation of the epithelium and a malodorous, profuse vaginal discharge. The papular and mucous membrane variants of lichen planus may coexist in one patient.

Severe itching may be present, especially with the papular variant, whereas burning, irritation, and dyspareunia are more common with erosive lichen planus, particularly when the vaginal area is involved. Characteristic areas of involvement in lichen planus that may yield diagnostic clues during the examination include the ventral aspect of the wrist (papular lichen planus) and the buccal mucosa (fernlike white papules).

The clinical diagnosis of lichen planus is made by finding typical fernlike white papules on the mucous membranes or modified mucous membranes of the buccal mucosa or vagina. A biopsy may be necessary to confirm the diagnosis.

Differential Diagnosis

The differential diagnosis of papular genital lichen planus includes a host of dermatologic conditions, including Bowen disease (vulvar intraepithelial neoplasia or penile intraepithelial neoplasia), psoriasis, and candidiasis. Erosive lichen planus may be mistaken for lichen sclerosus, cicatricial or bullous pemphigoid, or pemphigus.

Treatment

Papular lichen planus usually resolves over the course of years. Erosive lichen planus, especially severe forms, may lead to genital scarring, obliteration of the vaginal vault, or resorption of the genitalia. Topical, and occasionally oral, corticosteroids are often necessary to control disease. The patient should be referred to a dermatologist or gynecologist for optimal management.

Vesicles, Bullae, & Erosions

Erythema Multiforme, Stevens-Johnson Syndrome, & Toxic Epidermal Necrolysis

Essentials of Diagnosis

• • Rash characterized by targetoid lesions, with or without blisters, and frequent mucous membrane involvement.
• • Often associated with specific medications and herpesvirus infections.

Clinical Findings

Erythema multiforme is a dermatologic disease frequently encountered during the practice of medicine. It is characterized by targetoid lesions, with or without blisters, that tend to be in an acral distribution. Oral lesions and mucosal involvement may also be present, and it is possible for the rash to be confined to the palms, soles, and mucous membranes alone. Blisters located on mucosal surfaces erode quickly to form ulcers. Although lesions heal relatively quickly, scarring may result, especially when involvement is severe, as in Stevens-Johnson syndrome and toxic epidermal necrolysis.

Erythema multiforme may be associated with various medications and infectious processes. Recurrent erythema multiforme, for instance, is commonly associated with herpes simplex virus infections. Many experts think that erythema multiforme is on one end of a clinical spectrum, followed by Stevens-Johnson syndrome and toxic epidermal necrolysis, but this idea is controversial. Stevens-Johnson syndrome and toxic epidermal necrolysis are characterized by progressively increased mucosal involvement, widespread full-thickness epidermal necrosis and detachment (<10% for Stevens-Johnson syndrome and >30% for toxic epidermal necrolysis), and increasing mortality rates ranging from 5% for Stevens-Johnson syndrome to 40% for toxic epidermal necrolysis.

The diagnosis of erythema multiforme, Stevens-Johnson syndrome, or toxic epidermal necrolysis is made on the basis of the characteristic skin lesions, the extent of cutaneous and mucous membrane involvement, and the medication history. In the case of recurrent erythema multiforme, a history of recurrent herpes simplex virus infection is helpful. A biopsy may be necessary to confirm the diagnosis and rule out other etiologies.

Differential Diagnosis

Pemphigus vulgaris and bullous pemphigoid may be difficult to differentiate from blistering forms of erythema multiforme. Fixed drug eruption should also be considered in the differential diagnosis, although the number of lesions seen in a fixed drug eruption is usually far fewer than the number seen in erythema multiforme.

Treatment

Evaluation of patients presenting with symptoms consistent with these entities is urgent, because withdrawal of the offending drug is the most important aspect of treatment of drug-induced disease. In cases of recurrent erythema multiforme, suppression of herpes simplex virus is helpful, although the acute treatment of the virus is not as beneficial. Local care is important to prevent bacterial superinfection. The use of intravenous immune globulin has been reported to be helpful in more severe, blistering forms of erythema multiforme whereas corticosteroid use continues to be controversial.

Fixed Drug Eruption

Essentials of Diagnosis

• • Skin and mucous membrane lesions may be present.
• • Lesions recur at the same sites following rechallenge with the implicated drug.

Fixed drug eruption is a hypersensitivity reaction to a specific medication. Commonly implicated medications are listed in Table 30–3. Lesions vary in appearance depending on the type of epithelium involved. Lesions involving keratinized epithelium, for instance, appear as a well-demarcated, round, erythematous plaque whereas mucous membrane lesions blister and erode quickly. The glans penis is the most commonly involved genital site. Patients may complain of burning in the area of involvement. Rechallenge with the offending medication results in a recurrence of the lesions in the same places. The lesions frequently become more severe and result in more pronounced postinflammatory hyperpigmentation with each rechallenge.

Diagnosis is usually based on the appropriate clinical appearance in the setting of a consistent medication history. Biopsy is rarely needed but the histologic findings are characteristic. Recurrent herpes simplex virus, erosive lichen planus, and trauma are the primary etiologies to be considered in the differential diagnosis.

Withdrawal of the offending agent is the primary treatment, and lesions usually resolve within 7–10 days after removal of the agent. Local care may be necessary.

White Patches & Plaques

Lichen Sclerosus

Essentials of Diagnosis

• • The most common genital dermatosis characterized by white or hypopigmented lesions.
• • Women are affected more often than men.

Lichen sclerosus is a relatively common, often asymptomatic disorder that results in hypopigmentation, thinning of the skin, and increased tissue fragility. It most commonly affects the genitalia although other sites may be involved, including the trunk and arms. The etiology is unknown, but it has been associated with autoimmune diseases.

Findings on physical examination include white papules and plaques that are covered by atrophic skin having the consistency of cigarette paper. The lesions may become confluent, and the periclitoral area, labia minora, interlabial sulcus, perineum, and perianal area may become involved (see Figure 30–8). When all of these areas are involved, a classic figure-of-eight pattern may result. In men, involvement of the prepuce and glans are most common. Pruritus is the most common symptom. Due to tissue fragility, secondary changes may occur, including ecchymoses, erosions, and excoriations—findings that may be confused with sexual abuse, especially in children. Long-standing, poorly controlled lichen sclerosus is associated with genital scarring as well as an increased risk for squamous cell carcinoma.

The differential diagnosis of lichen sclerosus includes vitiligo, postinflammatory hypopigmentation, and the end stage of other poorly controlled genital dermatoses, including lichen planus and cicatricial pemphigoid.

The diagnosis may be made on a clinical basis but should be confirmed by biopsy. Patients should be referred to a dermatologist for management.

Scabies

Essentials of Diagnosis

• • Infestation caused by the mite Sarcoptes scabiei, with pruritus as its chief manifestation.
• • Frequent involvement of the genitalia, especially the glans penis and scrotum in men.

General Considerations

Scabies is a common dermatologic condition caused by the arthropod Sarcoptes scabiei and characterized by erythematous papular skin lesions accompanied by severe pruritus. Two primary types of skin eruptions are seen: (1) erythematous papular or vesicular lesions that are associated with burrows, and (2) a more generalized papular rash.

Clinical Findings

Symptoms and Signs

The eruption from scabies is most frequently observed in the interdigital web spaces, and on the wrists, anterior axillary folds, periareolar area in women, periumbilical skin, groin, pelvic girdle, and the glans penis in men (see Figure 30–9). The head and neck are typically spared. Although the etiology is the same, scabies affecting the glans penis and scrotum may appear more nodular (ie, nodular scabies) than eruptions elsewhere on the body.

The distribution of the rash, along with a history of pruritus that is more severe at night, serve as diagnostic clues. The burrow, made by the female mite, is the most classic diagnostic sign of scabies and appears as a grayish serpiginous line that may be difficult to visualize with the unaided eye. The severe pruritus is due to hypersensitivity to S scabiei and, therefore, although scabies may take 4–6 weeks to become symptomatic in individuals experiencing infestation for the first time, symptom onset occurs within 24 hours during subsequent infestations. The average burden on an immunocompetent host is approximately 10–12 mites and, once removed from the host, S scabiei is able to survive 24–36 hours at room temperature.

The appearance of scabies in an immunocompromised host may be atypical. Crusted or “Norwegian” scabies is a variant seen more frequently in patients with advanced HIV infection, human T-lymphotrophic virus type 1 infection, various hematologic malignancies, and organ transplant recipients, as well as in those who are malnourished, mentally retarded, or receive systemic or potent topical corticosteroids. Crusted scabies is characterized by thickened skin and hyperkeratotic warty crusts that are most predominant on the hands, feet, trunk, and scalp. However, the lesions may appear anywhere on the body. Sometimes the lesions of crusted scabies bear a resemblance to psoriasis. For this reason, new-onset psoriasis in an immunocompromised patient deserves a second look. Patients with crusted scabies may harbor millions of mites and are very infectious. Pruritus may be minimal or absent. Bacterial superinfection with typical skin pathogens (eg, Staphylococcus aureus and Streptococcus pyogenes) is a common complication of untreated scabies and, due to the compromised epidermal barrier, may lead to subsequent bacteremia and death.

Laboratory Findings

The diagnosis of scabies is based on a combination of clinical and laboratory findings. A presumptive diagnosis may be made based on the presence of a papular rash in the typical distribution, accompanied by pruritus that is worse at night. Parasitologic confirmation of the diagnosis may be made by removing the top of the burrow with a scalpel, placing the material on a slide containing 10% potassium hydroxide or mineral oil, and examining it under a low-power microscope for mites, eggs, egg cases, or fecal pellets.

Differential Diagnosis

Atopic dermatitis and seborrheic dermatitis are the primary conditions that may be confused with scabies. Crusted scabies may be confused with psoriasis, and insect bites may appear similar to nodular scabies.

Treatment

Pharmacotherapy

Options for the treatment of scabies include several topical medications and one oral agent. The current treatment of choice in the United States is permethrin cream 5%. A well-tolerated pyrethroid insecticide derived from chrysanthemums, permethrin is poorly absorbed across the skin and has a low toxicity profile. Permethrin is a pregnancy category B drug and can be used in pregnant women as well as in children and infants older than 2 months of age. In adults, permethrin cream should be applied from the neck down and washed off after 8–14 hours. In children younger than 5 years of age and the elderly, scabies infestation may involve the head; therefore, topical treatment should be applied to the entire skin surface except the eyes. Patients may experience mild itching and stinging on application. At present, permethrin resistance is not commonly encountered in the S scabiei mite, although continued surveillance for this potential problem is necessary.

Lindane (gamma benzene hexachloride 1%), an organochloride insecticide, has fallen out of favor because of problems with resistance and toxicity. Unlike permethrin, lindane is easily systemically absorbed when topically applied, especially in patients with widespread dermatologic conditions and in infants and children. Neurotoxicity (predominantly seizures) has occurred when lindane was applied following a bath, as well as in infants, children, the elderly, patients weighing less than 50 kg, and those with widespread skin damage. In addition, rare cases of aplastic anemia have been associated with lindane use. Lindane resistance has been well-documented; however, the drug is effective in most areas of the world. In adults, 1 oz of lindane 1% lotion or 30 g of cream should be applied in a thin layer to all areas of the body from the neck down and thoroughly washed off after 8 hours. Lindane should not be used immediately after a bath or shower and should be avoided in individuals with extensive dermatitis, pregnant or lactating women, and children younger than 2 years of age.

Ivermectin, a macrocyclic lactone antibiotic, is the only oral treatment option for scabies. Ivermectin has broad-spectrum activity against both nematodes and arthropods and results in a cure rate approaching 100% when given in two doses separated by 2 weeks. The currently recommended regimen is 200 mcg/kg orally, repeated in 2 weeks. Additional doses or a combination of oral and topical treatment may be necessary to control crusted scabies. Although one study demonstrated increased mortality among elderly patients who received ivermectin, this finding has not been confirmed by subsequent reports. Ivermectin is a pregnancy class C drug and is secreted in low concentrations in breast milk; it is therefore not currently recommended for use in pregnant and lactating women. The Food and Drug Administration has not labeled this drug for use in children weighing less than 15 kg.

Patients may continue to experience symptoms for up to 2 weeks after therapy. The primary reasons for persistent symptoms include incorrect initial diagnosis, ongoing hypersensitivity to the mite antigen, sensitization to the topical medication, reinfection from untreated contacts or contaminated fomites, treatment failure due to incorrect application of the medication or inadequate penetration of the topical medication into crusted areas, and drug resistance.

When symptoms continue 2 weeks after treatment, it is often unclear what should be done. If live mites are present, the need for retreatment is straightforward. Some clinicians proceed with retreatment in the absence of live mites, as reinfection is relatively common. The drug used for retreatment should be different than the drug used for initial therapy.

Other Measures

Because mites may survive up to 72 hours away from the human host, environmental measures are an important adjunctive to medical therapy. Therefore, bedding and clothing should be decontaminated, either through machine washing and drying using a hot cycle or by dry-cleaning. An alternative is to remove the clothing from body contact for at least 72 hours. It is unnecessary to fumigate living areas. In addition, because scabies is transmitted through close personal contact, including sexual contact, both sexual and close personal or household contacts within the preceding 30 days should be examined and treated.

Pubic Lice

Essentials of Diagnosis

• • An infestation caused by the crab louse, Phthirus pubis.
• • Pubic hair is the most common hair type involved.

Clinical Findings

Pubic lice, a common condition caused by the crab louse, Phthirus pubis, may lead patients to present for the evaluation of genital pruritus. The pubic louse, which is distinct from lice that infest the scalp (Pediculus humanus capitis) and the body (Pediculus humanus humanus), is 0.8–1.2 mm in length and can be seen with the naked eye (see Figure 30–10). The louse primarily infests pubic hair but may attach to adjacent hair of the chest, abdomen, legs, and buttocks. Eyelashes may also become infested.

Phthirus pubis lives for approximately 2 weeks, during which females produce about 25 ova. The nits incubate for 1 week, and the nymphs mature to adults over the subsequent 2 weeks. Because the accompanying pruritus results from hypersensitivity to louse saliva, it may be 2 or more weeks before symptoms develop following initial infestation. Bluish-gray macular lesions secondary to deep dermal hemosiderin deposition from the bites of the louse, known as maculae cerulean, may be noted in patients with established infestation.

Crab lice and nits may be seen with the naked eye; therefore, the presence of one or both of these forms in the hair is diagnostic. The presence of maculae cerulean may also provide a diagnostic clue.

Differential Diagnosis

Nits may be mistaken for white piedra and trichomycosis pubis. Pubic lice may cause a perifolliculitis that may be confused with bacterial folliculitis.

Treatment

Permethrin 1% cream rinse and pyrethrins with piperonyl butoxide are the primary agents recommended for the treatment of pubic lice and are the drugs of choice for pregnant or lactating women. These agents should be applied to the affected areas and washed off after 10 minutes. Resistance to pyrethrins has been documented, and the use of permethrin 5% may be necessary to overcome this problem, although experience with this higher concentration is largely anecdotal. Malathion 0.5% lotion is an alternative when treatment failure is thought to be secondary to drug resistance. The agent should be applied to the affected area for 8–12 hours and rinsed off. As noted earlier, lindane has fallen out of favor due to toxicity issues and should be used only as an alternative agent. If it is to be used, the 1% shampoo formulation should be applied for 4 minutes to the affected area and then thoroughly rinsed off. Lindane should not be used in children younger than 2 years of age or in pregnant or lactating women. Finally, ivermectin (200 mcg/kg as a single dose, repeated in 2 weeks), provides an oral alternative for therapy. When eyelash infestation is present, an occlusive agent such as petroleum jelly should be applied twice daily for 10 days. If symptoms persist after 1 week of treatment, the patient should be evaluated. If lice are found or nits are present at the hair-skin junction, retreatment should be initiated with an alternative agent.

Pubic lice are primarily spread through sexual contact. Therefore, all partners with whom the patient has had sexual contact within the previous 30 days should be evaluated and treated, and sexual contact should be avoided until all partners have successfully completed treatment and are thought to be cured. Because of the strong association between the presence of pubic lice and classic STDs, patients diagnosed with pubic lice should undergo evaluation for other STDs. Bedding and clothing should be decontaminated or removed from body contact for at least 72 hours.

• • Pearly penile papules are sometimes confused with condylomata acuminata. Unlike pearly penile papules, however, condylomata acuminata often have spiked tips or are contiguous at the base.
• • If the lesion of molluscum contagiosum is incised, a central core, usually waxy, can be expressed. The central umbilication and waxy core help differentiate molluscum contagiosum from other diseases.
• • Nail findings should be sought during the clinical evaluation of the patient with suspected genital psoriasis, because they may provide helpful diagnostic clues, especially given the often less characteristic qualities of the genital rash.
• • Characteristic areas of involvement in lichen planus that may yield diagnostic clues during the examination include the ventral aspect of the wrist (papular lichen planus) and the buccal mucosa (fernlike white papules).