CASE #2: Isolated lichen planus of the penis

The characteristics of lichen planus (LP) can be recalled by remembering the Ps: purple, polygonal, polymorphous, pruritic, and papular with polished surfaces. LP is seen most often on the wrists and arms but is not uncommon on the genitals and mucous membranes (where it looks white). In the mouth, the white manifestations of LP can appear reticulated and are referred to as Wickham’s striae.

LP can be diagnosed clinically, but biopsy is helpful. In erosive disease, even if the clinical impression is of Wickham’s striae, mouth lesions should be biopsied, particularly in smokers. In bullous LP, the clinical impression is usually of such diseases as bullous pemphigoid or pemphigus vulgaris, and only histologic examination reveals the true diagnosis.

Pathologically, lymphocytes attack keratinocytes and lead to an interface dermatitis. Degenerative keratinocytes, referred to as colloid or Civatte bodies, manifest in the lower epidermis. Direct staining by immunofluorescent techniques may reveal immunoglobulin deposits at the base of the epidermis. While the cause of LP is not known, some immune basis seems likely, and haplotype B7 is more common in patients with LP. Some association between LP and hepatitis C has been observed, particularly in Japan. Therefore viral induction of the pathologic process of LP is possible.


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LP has many variants. Hypertrophic LP often appears on the shins and can resemble prurigo nodularis. In men, erosive LP has a greater likelihood of inducing cancer. LP of the mucous membranes is present in about 50% of cases. LP follicularis, which involves the scalp, can lead to a scarring alopecia that manifests with small red spiny papules around a cluster of hairs. Atrophic LP looks more white than purple. LP pigmentosus is more common in darker-skinned individuals and can lead to brown and purple discoloration. LP pemphigoides is an overlap of LP and bullous pemphigoid. Linear LP must be distinguished from lichen striatus, linear psoriasis, and linear porokeratosis. LP of the nail is present in about 10% of cases and can cause pitting, grooving, and ridging of the nails. There can also be onycholysis. LP of the nails overlaps with 20-nail dystrophy (which can also be the result of alopecia areata) and can lead to scarring of the nail, including the formation of a pterygium, a scarring process on the underside of the nail. Vaginal LP can lead to scarring of the vagina, impairing sexual activity. Other variants include actinic, annular, and bullous LP.

The onset of LP can be sudden or gradual. Its incidence is the same in both sexes. LP is most common in middle age (30-70 years) but can occur at any age.3 Most cases of LP will resolve, unlike diseases such as psoriasis or lupus that can linger for a lifetime. The differential diagnosis of LP includes bullous diseases, dermatofibromas, lichen sclerosus, graft-versus-host disease, psoriasis, lichen nitidus, prurigo nodularis, syphilis, pityriasis rosea, and tinea. Drugs can cause a rash that resembles LP; this is called a lichenoid drug eruption. The most common causes of lichenoid drug eruptions are gold, antimalarial agents, and captopril. Actinic lichenoid drug eruptions, which occur in sun-exposed areas, are caused by antimalarials and thiazide diuretics.

Treatment of limited LP comprises topical steroids.4 Extensive LP can be treated with oral steroids, UV phototherapy, and oral acitretin. Methotrexate and hydroxychloroquine are also used for extensive cases of LP. Topical calcineurin inhibitors can be used to treat oral and erosive LP. Lichen planopilaris, which occurs in the scalp, is commonly treated with injection of corticosteroids.

In this case, a clinical diagnosis of LP was made; the patient declined biopsy of the lesion. After four weeks of treatment with triamcinolone 0.1% cream, the lesion had resolved, leaving behind some pigmentary alteration. n

Dr. Scheinfeld is assistant clinical professor of dermatology at Columbia University in New York City, where he has a private practice.

References

1. Armstrong DK, Irvine A, Walsh MY, et al. Multiple dermatofibromas in a patient with HIV infection. Clin Exp Dermatol. 1995;20:474-476.

2. Lu I, Cohen PR, Grossman ME. Multiple dermatofibromas in a woman with HIV infection and systemic lupus erythematosus. J Am Acad Dermatol. 1995;32(5 Pt 2):901-903.

3. Milligan A, Graham-Brown RA. Lichen planus in children—a review of six cases. Clin Exp Dermatol. 1990;15:340-342.

4. Gorouhi F, Solhpour A, Beitollahi JM, et al. Randomized trial of pimecrolimus cream versus triamcinolone acetonide paste in the treatment of oral lichen planus. J Am Acad Dermatol. 2007;57:806-813.