The classic cutaneous lesion of lichen planus is a faintly erythematous to violaceous, flat-topped, polygonal papule, sometimes showing a small central umbilication (Fig. 26-1). Papules are grouped and tend to coalesce. A thin, transparent, and adherent scale may be discerned atop the lesion. Fine, whitish puncta or reticulated networks referred to as Wick-ham striae are present over the surface of many well-developed papules (see Fig. 26-1). These are considered to be highly characteristic and are more easily observed after applying oil, xylene, or water and visualizing the lesions with a magnifying lens or a handheld dermatoscope. The surface alteration may result from localized thickening of the keratohyalin-containing cell layers of the stratum granulosum, although a focal increase in the activity of lichen planus may account for the morphologic alteration of Wickham striae.
Flat-topped, polygonal, sharply defined papules of violaceous color, grouped and confluent. Surface is shiny and reveals fine white lines (Wickham striae). Note pigmentation of resolving lesions.
Lichen planus usually develops over several weeks. Sometimes multiple lesions develop rapidly with dissemination following the initial appearance. In generalized disease (Fig. 26-2), the eruption often spreads within 1–4 months from onset. The initial lesions almost always appear on the extremities, especially the legs.
Generalized lichen planus. Small, flat-topped violaceous papules, some grouped, some disseminated, becoming confluent on the trunk.
The lesions are usually distributed symmetrically and bilaterally over the extremities. Lichen planus tends to involve the flexural areas of the wrists, arms, and legs (see Fig. 26-1). The thighs, lower back, trunk, and neck may also be affected. Oral mucous membranes (Fig. 26-3) and the genitalia (Fig. 26-4) are additional sites of involvement. The face is usually spared in classical cases, and palmoplantar involvement is unusual. Inverse lichen planus usually affects the axillae, groin, and inframammary areas.
Mucosal lichen planus. A. A typical lace-like whitish reticulated pattern of oral lesions is seen on the buccal mucosa. B. Erosive gingivitis. Here lichen planus manifests as painful erosions on the gingiva.
Lichen planus on the penis. Agminate pattern of lesions involving the glans, sulcus, and meatus (not seen) of the penis.
Lichen planus tends to be quite pruritic, although some patients are completely asymptomatic. The degree of pruritus is generally related to the extent of involvement, with more intense pruritus in generalized form. An exception is hypertrophic lichen planus, which is more localized but extremely pruritic. Oral involvement is generally asymptomatic unless erosions or ulcers developed, after which it becomes extremely painful. In the acute, evolving stages of the disease, scratching, injury, or trauma may induce an isomorphic (Koebner) response (Fig. 26-5). Lichen planus usually heals with hyperpigmentation (see Fig. 26-1), which is more prominent among patients with darker skin color. Hypopigmentation uncommonly develops after resolution of lesions.
Lichen planus. Linear pattern with Koebner response adjacent to clustered papules on the flexural wrist.
Most reports of lichen planus in children have come from the Indian subcontinent, suggesting that children of South Asian origin are more susceptible to developing lichen planus.15 Although the clinical and pathologic features of childhood lichen planus are similar to those in adults, scalp, nail, and hair involvement are not common. Mucous membrane involvement, thought to be rare, may occur in up to one-third of patients. The hypertrophic variant occurs in one-fourth of children with lichen planus.
Many variations in the clinical presentation have been described and are generally categorized according to (1) the configuration of lesions, (2) the morphologic appearance, or (3) the site of involvement. These variations are patterned by subtle or unknown properties of the disease. The prototypic papule can be altered or modified in configuration, morphology, or anatomic distribution.
Annular lesions occur in approximately 10% of cases and commonly develop as arcuate groupings of individual papules that develop rings or peripheral extension of clustered papules with central clearing. They tend to occur in blacks and are more common on the penis and scrotum (see Chapter 75). It occurs also when larger lesions on trunk and extremities reach 2–3 cm in diameter and become hyperpigmented with a raised outer rim. Actinic lichen planus (see below), seen in subtropical zones on sun-exposed, dark-skinned young adults and children, is frequently annular in shape.
Papules of lichen planus may develop a linear pattern secondary to trauma (koebnerization) (see Fig. 26-5) or, rarely, in less than 0.2% of cases as a spontaneous, isolated eruption, usually on the extremities following Blaschko lines. The segmental formation is thought to be due to a postzygotic mutation that affects one of the genes predisposing its development that lead to the formation of a keratinocyte clone that is more susceptible to development of lichen planus.16 Drug-induced linear lichen planus has also been reported.17,18
It is important to differentiate linear lichen planus from nevus unius lateris, lichen striatus, inflammatory linear verrucous epidermal nevus, linear psoriasis, and linear Darier–White disease, which have different presentations clinically and histopathologically.
Hypertrophic Lichen Planus
Hypertrophic lichen planus (lichen planus verrucosus) usually occurs on the extremities, especially the shins and interphalangeal joints, and tends to be the most pruritic variant (Fig. 26-6).19 Lesions are thickened and elevated, purplish or reddish-brown in color, and hyperkeratotic. Occasionally, verrucous plaques develop. Lesions may show accentuated and elevated follicular induration and chalk-like scale. This variant usually heals with scar formation and hyper- or hypopigmentation. Chronic venous insufficiency is frequently present.
Hypertrophic lichen planus in the pretibial region of a dark-skinned individual. Lesions are almost nodular and very dark with the violaceous sheen of lichen planus. Lesions may later become hyperkeratotic.
The atrophic variant is rare and is characterized by the presence of a few well-demarcated, white-bluish papules or plaques, sometimes more erythematous, with central superficial atrophy.2 The lesions are a few millimeters wide but may coalesce to form larger plaques. They are most common on the lower extremities or trunk. The lesions often resemble lichen sclerosus et atrophicus. However, the histologic features are diagnostic.
Vesiculobullous Lichen Planus
The development of vesicles and bullae in lichen planus is rare. (Fig. 26-7). The bullae, which appear most commonly on the extremities, arise from existing papules of lichen planus and rarely from normal-appearing skin. They may appear suddenly during an acute flare of disease and are usually associated with mild constitutional symptoms. These lesions usually resolve in a few months. Bulla arising in oral lichen planus can lead to painful erosions. Histologically, subepidermal separation is present in addition to typical features. Bullae formation does not necessarily indicate a longer duration of the disease. Bullae arising from normal skin are more characteristic of lichen planus pemphigoides and should be differentiated by direct and indirect immunofluorescence (see below).
Vesiculo-bullous lichen planus. Vesicles and bullae with violaceous-erythematous papules and plaques on the foot.
Erosive and Ulcerative Lichen Planus
A rare variant presents with chronic, painful bullae and ulcerations of the feet with often, cicatricial sequelae (Fig. 26-8). Patients typically have nails, and mucosal involvement in addition to classical skin lesions, which often aids in establishing the diagnosis. Permanent loss of toenails and cicatricial alopecia of the scalp are common. Squamous cell carcinoma (SCC) may develop in lesions of ulcerative lichen planus.20
Erosive–ulcerative lichen planus showing erosions, ulcers, and granulation tissue and scarring of toes, interdigital web spaces, and soles.
Erosions and ulcerations may also develop in more severe cases of oral lichen planus.
Follicular lichen planus may occur alone or in association with other forms of cutaneous or mucosal lichen planus.16 The term lichen planopilaris has been used to describe this distinctive variant, but other terms include lichen planus follicularis, peripilaris, and acuminatus. Individual keratotic follicular papules and studded plaques are seen. Sites of predilection include the trunk and medial aspects of the proximal extremities.21 Follicular lichen planus may affect the scalp with the development of cicatricial alopecia (see Section “Lichen Planus of the Scalp”; Fig. 26-9). The triad of follicular lichen planus of skin (lichen planus spinulosus) and/or scalp, multifocal cicatricial alopecia of the scalp, and nonscarring alopecia of the axillary and pubic areas, has been described as Graham–Little–Piccardi–Lassueur (or Graham–Little–Feldman) syndrome. Sometimes more typical lesions of the skin and nails are seen. Other variants of follicular lichen planus include the lichen planus follicularis tumidus with oval pseudotumoral plaques of the mastoid area, postmenopausal frontal fibrosing alopecia,22 and lichen planoporitis, with the lichenoid reaction centered over the acrosyringium and eccrine ducts entering the epidermis.
Lichen planus. A. Irregular patches of alopecia with violaceous papules and coalescing plaque of lichen planus within scalp. B. Lichen planopilaris resulting in atrophic, scarred, porcelain-colored area centrally with bordering follicular involvement consisting of dusky erythema, perifollicular hyperkeratosis and scale, and follicular convergence resulting in doll's hair formation. C. Extensive hair loss leading to pseudopelade of Brocq appearance. Several remaining tufts of hair showing violaceous erythema and disease activity.
Lichen Planus Pigmentosus
This variant is characterized by hyperpigmented, dark-brown macules in sun-exposed areas and flexural folds. This entity tends to occur in patients with darker pigmented skin. Histologically, an atrophic epidermis, a vacuolar alteration of the basal cell layer with a scarce lymphohistiocytic lichenoid infiltrate, and pigment incontinence are seen. This variant bears significant similarity to ashy dermatosis or erythema dyschromicum perstans. It may represent an overlap in the phenotypic spectrum of lichenoid inflammation in darkly pigmented skin, with ethnic and genetic factors influencing the expression of disease (see Chapter 75).23 In cases where the inflammatory phase was minimal, such as lichen planus “invisible de Gougerot,” the pigmentation may be the only sign of the disease.
Also known as lichen planus subtropicus, lichen planus tropicus, summertime actinic lichenoid eruption, lichen planus actinicus, lichen planus atrophicus annularis, and lichenoid melanodermatosis. Actinic lichen planus affects young people of the Middle East in spring and summer, where sunlight appears to have a precipitating effect. Exposed areas of the face, dorsal hands and arms, and the nape of the neck are usually affected. Papules are hyperpigmented with violaceous-brown color and a thready, rolled edge showing well-defined borders. Annular lesions are common, but pigmented and linear forms were seen.24,25 Typical lichen planus lesions may be present over the extremities. Pruritus and scaling are minimal.
A perforating variant has been described in which transepidermal elimination of lichen planus-like inflammatory tissue is observed. Guttate lichen planus is another variant that resembles guttate psoriasis but with the characteristic lichenoid histology. Exfoliative and exanthematous forms are very rare and may represent manifestations of lichenoid drug reactions (Fig. 26-10). The rare entity of invisible lichen planus describes lesions that are not perceptible with visible light illumination but become apparent with Wood's lamp examination. Pruritus is present and biopsy evaluation shows lichenoid histology. This entity may be a minimal variant of lichen planus “invisible de Gougerot.”
Lichen planus-like eruption. Generalized violaceous papules with superficial scale coalescing to form erythematous variant. History of associated drug exposure leading to lichenoid reaction.
Lichen Planus of the Scalp
Lichen planopilaris (LPP) or follicular lichen planus may affect the scalp in a distinctive clinical and histologic pattern that affect women more than men.26–30 LPP can be subdivided into three variants: (1) classic LPP, (2) frontal fibrosing alopecia, and (3) Lassueur–Graham–Little–Piccardi syndrome. In classic LPP, individual keratotic follicular papules that coalesce and merge over the scalp to form patches are typically seen. Perifollicular erythema and acuminate keratotic plugs are characteristic features. Follicular-centered lesions are usually observed under close inspection of the scalp and orifices, particularly at the margins of the alopecic area or within patches still bearing hair. Cutaneous, nail, or mucous membrane involvement with lichen planus may also be present. Patients present with uni- or multifocal hair loss that may be extensive and sometimes involve the entire scalp (see Fig. 26-9). The condition can have major psychological impact on affected individuals.
End-stage disease is characterized by a nondescript scarring alopecia that has led to the use of several clinical terms describing the entity: lichen planopilaris, folliculitis decalvans et atrophicus, lichen spinulosus at folliculitis decalvans, and Graham–Little syndrome.
Frontal fibrosing alopecia is an uncommon condition characterized by progressive frontotemporal recession due to inflammatory destruction of hair follicles. It is more common in postmenopausal women, but it can occur in younger women. It may be associated with mucocutaneous lichen planus. Recession of the hairline may progress inexorably over many years, but this is not inevitable.22,31
Pseudopelade of Brocq is a rare clinical syndrome of scarring alopecia and fibrosis, in which distinct pathologic features are absent. It is generally accepted that pseudopelade of Brocq is the end stage of follicular fibrosis caused by a primary inflammatory dermatosis such as lichen planus, lupus erythematosus, pustular-scarring forms of folliculitis, or fungal infections, including favus, scleroderma, and sarcoidosis.
Lichen planus can affect the mucosal surfaces of mouth, vagina, esophagus, conjunctiva, urethra, anus, nose, and larynx. Its prevalence is estimated at approximately 1% of the adult population. Oral involvement occurs in approximately 60%–70% of patients with lichen planus. It may be the only manifestation in 20%–30% of patients.
In oral lichen planus, different types have been described, including reticular, plaque-like, atrophic, papular, erosive/ulcerative, and bullous forms (see Fig. 26-3).32,33 The reticular pattern is considered the most common, but patients with erosive form are more likely to seek medical help due to the symptomatology (pain and burning sensation) and chronicity. Most patients have more than one type. The buccal, gingival, and glossal mucosae are the most commonly affected areas. The palate, floor of the mouth, retromolar pads, and lips may also be affected. Gingival involvement may take the form of gingival stomatitis or desquamative gingivitis, and could be the sole presentation in 8% of oral lichen planus. On the other hand, lichen planus is the most common cause for desquamative gingivitis.34
Oral lichenoid reaction is similar clinically and histologically to oral lichen planus, however, with identifiable etiology. Differentiating these two entities is often difficult. It is usually seen on the buccal mucosa adjacent to amalgam dental fillings.35,36 Patch tests frequently show positive reactions to mercury, gold, and other metals.37,38
Bilateral reticular keratotic or atrophic changes of the buccal mucosa and lichenoid atrophic patches over the dorsal tongue have been described in patients with HIV infection. The eruptions usually follow zidovudine or ketoconazole intake.
Esophageal Lichen planus is rare and affects the proximal esophagus. It manifests as progressive dysphagia and odynophagia. Endoscopic findings can include lacy white papules, pinpoint erosions, desquamation, pseudomembranes, and stenosis. Histologically, it shows parakeratosis, epithelial atrophy, and lack of hypergranulosis. Squamous cell carcinoma of esophagus may develop after longstanding disease.39,40
Male genitalia are involved in 25% of cases, and the glans penis is most commonly affected, with annular lesions frequently present (see Fig. 26-4). Anal lesions of mucosal lichen planus present with leukokeratosis, hyperkeratosis, fissuring, and erosions (Fig. 26-11).
Lichen planus. Perianal leuko- and hyperkeratosis with hypertrophic, folded violaceous epithelium, fissures, and healing biopsy site.
Vulvar and vaginal lichen planus is present in over half of patients with oral lichen planus.41 Clinically, the condition is often asymptomatic unless erosions develop. Burning, itching, pain and abnormal discharge then become common.42 Examination reveal patches of leukoplakia or erythroplakia, sometimes with erosions, and, occasionally, as a more generalized desquamative vaginitis. Vaginal adhesions and labial agglutination may result.
The vulvo-vaginal gingival syndrome is characterized by involvement of vulvar and gingival tissues. Erythema and erosions of the gingivae and tongue and, occasionally, white reticulated plaques, is associated with desquamation and erosions of vulva and vagina.43
Conjunctival lichen planus may manifest as cicatricial conjunctivitis. Histologically, irregular thickening with reduplication of the basement membrane is seen. Direct immunofluorescence distinguishes ophthalmic lichen planus from cicatricial pemphigoid.
Lichen Planus of the Nails
(See also Chapter 89.) Nail involvement occurs in 10%–15% of patients.44 Lichen planus limited to the nails is uncommon, and the initial involvement is followed, in many cases, by the development of typical lesions elsewhere. Lichen planus of nails is infrequent in children. Thinning, longitudinal ridging, and distal splitting of the nail plate (onychoschizia) are the most common findings. Onycholysis, longitudinal striation (onychorrhexis), subungual hyperkeratosis, or even absence (anonychia) of the nail plate can also be seen. Twenty-nail dystrophy (trachyonychia) may represent an isolated nail finding of lichen planus. Psoriasis and alopecia areata can also lead to these distinctive nail changes. Nail loss may result from ulcerative lichen planus involving the nail unit. Pterygium or forward growth of the eponychium with adherence to the proximal nail plate is a classic finding of lichen planus of the nail (Fig. 26-12). An atrophic cicatrizing form of lichen planus with random and progressive nail loss in Asians and blacks has also been reported. The tenting or pup-tent sign is observed as a result of nail bed involvement that elevates the nail plate and may cause longitudinal splitting.2
Lichen planus. Classic pterygium formation and tenting of several fingers with loss of nail plates.
The inverse pattern occurs only rarely and is characterized by red-brownish, discrete papules, and nodules. The eruption occurs mainly in the flexural areas such as axillae, inframammary, groin, and, less likely, the popliteal and antecubital areas. Koebnerized lesions are occasionally present.
Palmoplantar Lichen Planus
This is a rare variant that is difficult to diagnose if present as an isolated finding. Very pruriginous, erythematous, scaly plaques with or without hyperkeratosis are characteristic. Lesions are often seen on the internal plantar arch. Yellowish, compact keratotic papules or papulonodules are seen on the lateral margins of the fingers and hand surfaces; however, they are less likely to affect the fingertips. They appear like callosities with an inflammatory, erythematous halo. The lesions resemble psoriasis vulgaris, warts, calluses, porokeratosis, hyperkeratotic eczema, tinea, or secondary syphilis.45 Palmoplantar lichen planus may also present as erosive–ulcerative type (see Section “Erosive and Ulcerative Lichen Planus”).
Special Forms of Lichen Planus or Lichenoid Eruptions
Drug-Induced Lichen Planus
Lichen planus-like or lichenoid eruptions describe a group of cutaneous reactions identical or similar to lichen planus (see Fig. 26-10).46 Lichenoid drug eruptions have been reported after ingestion, contact, or inhalation of certain chemicals (Table 26-1). They may be localized or generalized with eczematous papules and plaques and variable desquamation. They typically manifest postinflammatory hyperpigmentation and alopecia, and do not exhibit classic Wickham striae. The eruptions usually appear symmetrically on the trunk and extremities, unlike the flexural distribution of classic lichen planus. Mucous membrane involvement is less common and is often associated with specific drugs and chemicals. A photodistributed pattern is often found in sun exposed areas, and several drugs frequently induce this reaction (see Table 26-1).
Table 26-1 Agents Inducing Lichen Planus and Lichenoid Reactions
The latency period for development of a lichenoid drug eruption by these agents varies from months to a year or more based on the dosage, host response, previous exposure, and concomitant drug administration. Resolution of the eruptions is quite variable, but most disappear in 3–4 months, except in gold-induced lichenoid eruption that may require up to 2 years after discontinuation. For many inciting drugs, the severity and extent of the eruption influences the rate of clearance. Occasionally, the lichenoid drug eruption disappears or may recur intermittently despite continuation of treatment.
Lichenoid contact dermatitis may result from contact with compounds such as color film developers, dental restoration materials, metals (e.g., mercury, silver, and gold), and aminoglycoside antibiotics.46 Oral lichenoid drug eruptions are mostly related to dental restoration metals such as mercury, silver, and gold.
Lichen Planus–Lupus Erythematosus Overlap Syndrome
This is a rare variant characterized by lesions that share features of lichen planus and lupus erythematosus. Atrophic plaques and patches with hypopigmentation and a livid red to blue–violet color with telangiectasia and minimal scaling are characteristic. Transient bullae may develop. Classic lesions of lichen planus, photosensitivity, pruritus, and follicular plugging are also not common. Lesions may develop anywhere, but are most common on the extremities (Fig. 26-13). Some patients with this overlap syndrome may progress to systemic lupus erythematosus. In other instances, laboratory evaluation may reveal only a weak-positive antinuclear antibody. This disease variant is characterized by a prolonged course and lack of response to treatment. Histologically, a lichenoid reaction typical for lichen planus and histologic features of lupus erythematosus are usually present in the same biopsy.47 By direct immunofluorescence, cytoid bodies staining with IgG, IgM, and C3 intraepidermally or at the dermal–epidermal junction, as seen in classic lichen planus, are most common. Linear to granular deposition of IgM and C3 (as seen in lupus erythematosus, but not in lichen planus) and shaggy deposition of fibrinogen at the basement membrane zone, typical of lichen planus have been observed occasionally.47
Lichen planus–lupus erythematosus overlap syndrome. Lichenoid lesions involving dorsal hand and forearm with direct immunofluorescence evidence of lupus erythematous.
Lichen Planus Pemphigoides
Lichen Planus Pemphigoides is characterized by the development of tense blisters atop lesions of lichen planus or the development of vesicles de novo on uninvolved skin or oral mucosa (Fig. 26-14). It is important to differentiate this entity from bullous lichen planus, in which blisters develop in lesions of long-standing lichen planus as a result of intense lichenoid inflammation and extensive liquefaction degeneration of basal keratinocytes. The etiology of this variant is not clear. It was proposed that basal cell keratinocyte damage by lymphocytes in lichen planus may unmask hidden antigenic determinants and lead to autoantibody formation and induction of bullous lesions. Captopril was described to induce this entity also.48 Histologic findings resemble those of lichen planus. Direct immunofluorescence shows linear deposition of IgG and C3 at the dermal–epidermal junction.49 Sera from these patients react with the epidermal side of NaCl-split human skin. Circulating IgG autoantibodies react to the major noncollagenous extracellular domain (NC16A) of the 180-kDa bullous pemphigoid antigen within the basement membrane zone. Further mapping showed that lichen planus pemphigoides serum reacts with amino acids 46–59 of domain NC16A, a protein segment that was previously shown to be unreactive with bullous pemphigoid sera. This newly described epitope is designated MCW-4.50
Lichen planus pemphigoides. Lichenoid maculopapular erythema, erosions, and bullae with direct immunofluorescence showing features of bullous pemphigoid. Indirect immunofluorescence also was positive.
Keratosis Lichenoides Chronica (Nekam Disease)51
Lichenoid Reaction of Graft‐versus-Host Disease
Chronic graft-versus-host disease (GVHD) (occurring 100 days after transplant) may present as a lichenoid eruption indistinguishable clinically and histologically from lichen planus. Lichenoid GVHD favors the trunk, buttocks, hips, thighs, palms, and soles. In oral mucosa, xerostomia and oral ulcerations are occasionally seen. Histologically, the findings in lichen planus and oral GVHD are similar, although more infiltrating CD3+ T lymphocytes are present in oral lichen planus than in GVHD.52 Natural killer cells, Leu-8-positive T cells (homing receptor: CD62L, LECAM), CD25-positive lymphocytes, and the CD4:CD8 ratio were not different. Langerhans cells are often increased in both conditions.
Lichenoid keratoses are brown to red, scaling maculopapules found on sun-exposed skin of extremities. Histologic features of lichen planus are present, with the additional finding of focal parakeratosis. They frequently occur with solar lentigo, seborrheic keratosis, and actinic keratosis and likely represent an “involuting lichenoid plaque.”53