Purple papules in an arcuate pattern on the genitalia


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An African-American man, aged 35 years, presents with a 3-month history of pruritic penile lesions. Examination reveals an arcuate pattern of raised violaceous-to-flesh-colored papules with central clearing on the glans penis and a few scattered, raised violaceous-to-flesh-colored polygonal papules of the glans penis and distal penile shaft. Results of the remainder of the skin examination are normal, and there is no inguinal lymphadenopathy. His sexual history includes no previous sexually transmitted diseases and no new sexual partners within the past year. 

Lichen planus is an acutely occurring inflammatory skin disease characterized by a papulosquamous eruption of the skin, scalp, nails, and mucous membranes.1 Lichen planus has an estimated frequency of approximately 1% in the general population.2Approximately 25% of men with lichen...

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Lichen planus is an acutely occurring inflammatory skin disease characterized by a papulosquamous eruption of the skin, scalp, nails, and mucous membranes.1 Lichen planus has an estimated frequency of approximately 1% in the general population.2

Approximately 25% of men with lichen planus have lesions on the genitalia; the glans penis is the most commonly affected area.3One study of women with oral lichen planus found that more than 75% also had genital involvement, and half of these cases were asymptomatic.4 In consideration of this statistic, it is important that all patients with lichen planus should undergo a systematic genital examination, especially those with involvement of the oral mucosa.2

The classic presentation of cutaneous lichen planus is characterized by the “4 Ps”: purple, polygonal, pruritic, papules.5 However, the most common clinical expression of genital lichen planus is leukokeratotic lesions, consisting of flat, white papules that coalesce into compact patches or networks.2 The lesions may also manifest similar to the classical cutaneous description described in the introductory case or as arcuate groupings of individual papules that develop rings or peripheral extension of clustered papules with central clearing.3 Fine white streaks (Wickham striae) may appear on the surface of the lesions. In uncircumcised patients, the lesions assume a lacy, white, reticulated pattern.1 Genital lichen planus often has a dominant erosive component, which is much more frequent in women and varies in intensity and area.2 Erosive lichen planus in men mainly affects the glans, manifesting as bright red lesions that must be differentiated from Zoon balanitis.2

Patients with lichen planus often complain of pruritus and soreness. Lesions may be associated with ulceration or induration, which may suggest squamous cell carcinoma and require biopsy.1

Although its pathogenesis is not fully understood, there is evidence that an imbalance of immunologic cellular reactivity is central.5 One theory includes an autoimmune reaction in which CD8+ T lymphocytes attack basal keratinocytes leading to the apoptosis of these basal cells.6 Various potential triggers of this autoimmune reaction include viral or bacterial antigens, metal ions, drugs, or physical factors. One frequently cited trigger includes the hepatitis virus (hepatitis B and hepatitis C virus), due to its association with mucosal lichen planus, including the genital mucosa.2 The incidence of mucosal lichen planus seen with hepatitis infection or carrier status varies, but is particularly significant in geographical areas where there is a high frequency of hepatitis virus infections.2 On this basis, it is advisable to test all patients with genital lichen planus, especially those with erosive lesions, for markers of viral hepatitis.

Clinical variants of lichen planus include annular, hypertrophic, atrophic, ulcerative, bullous, lichen planus pemphigoides, lichen planus pigmentosus, erythrodermic, inverse, linear, follicular, and actinic.6 These variants can be distinguished from the classical form of lichen planus based on morphology and distribution. Diagnosis of variants may be ensured with biopsy, which demonstrates the same characteristic histology of classical lichen planus.6

Diseases of the male genitalia range from infectious lesions to inflammatory and neoplastic conditions. Differential diagnosis of lichen planus affecting the genitalia should include common sexually transmitted diseases (herpes simplex viral lesions, primary syphilis), other inflammatory disorders (guttate psoriasis, lichen nitidus, lichenoid drug eruption), scabies infestation, and Zoon balanitis. 

The diagnosis of genital lichen planus is easy for the classical forms, especially when associated with oral localizations. Biopsy may, however, be necessary in the event of a questionable diagnosis; the lesional specimen should be taken from the edge of any eroded areas.2 The histopathologic findings of lichen planus include orthohyperkeratosis, circumscribed wedge-shaped hypergranulosis (representing histopathologic substrate of the Wickham striae), and sawtooth-like acanthosis of the epidermis. In the upper dermis, a band-like infiltrate (primarily lymphocytes) with possibly scattered histiocytes and neutrophils is seen. Vacuolar degeneration is observed along the dermoepidermal junction with colloid bodies (apoptotic keratinocytes).6

The diagnosis and management of penile cutaneous lesions can be challenging because of a lack of familiarity and patient embarrassment. Despite these challenges, many penile lesions can be diagnosed and managed by primary care providers. Response to treatment of lichen planus is variable, and the condition usually spontaneously resolves within a few months.5 Daily potent topical corticosteroids are usually effective but carry a risk of atrophy; however, weekend dosing of ultrapotent topical corticosteroids may be effective. These treatments have been shown to expedite recovery and alleviate symptoms.5 For isolated lichen planus of the prepuce, circumcision is indicated when medical management fails.1 Resolution of lesions may be accompanied by postinflammatory hyperpigmentation.5

For the patient in our case, a biopsy of the genital lesions confirmed the diagnosis of lichen planus. Topical triamcinolone 0.1% ointment was prescribed, and the lesions resolved by the 2-month follow-up.

Nicole R. Bender, MD, is an internal medicine intern in the dermatology residency 
program at the Medical College of Wisconsin in Milwaukee, and Maura Holcomb, MD, is a dermatology resident at Baylor College of Medicine in Houston.


  1. Teichman JM, Sea J, Thompson IM, Elston DM. Noninfectious penile lesions. Am Fam Physician. 2010;81(2):167-174.
  2. Andreassi L, Bilenchi R. Noninfectious inflammatory genital lesions. Clin Dermatol. 2014;32(2):307-314.
  3. Buechner SA. Common skin disorders of the penis. BJU Int. 2002;90(5):498-506.
  4. Di Fede O, Belfiore P, Cabibi D, et al. Unexpectedly high frequency of genital involvement in women with clinical and histologic features of oral lichen planus. Acta Derm Venereol. 2006;86(5):433-438.
  5. Sharma A, Bialynicki-Kirula R, Schwartz RA, Janniger CK. Lichen planus: an update and review. Cutis. 2012;90(1):17-23.
  6. Wagner G, Rose C, Sachse MM. Clinical variants of lichen planus. J Dtsch Dermatol Ges. 2013;11(4):309-319.
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