Should this penile rash prompt a search for other lesions?

Case 1:

For 2 months, a 27-year-old man has had this worsening rash on the head of the penis. He denies any history of trauma. What do you suspect?

A. Psoriasis.
B. Seborrhea.
C. Reiter syndrome.
D. Trauma.
E. Lichen planus.

Answers on next page

Psoriasis, A, is essentially an inflammatory skin disorder that is characterized by reactive abnormal epidermal differentiation and hyperproliferation. The underlying inflammatory mechanisms are most likely initiated and maintained primarily by T cells in the dermis.

Inverse psoriasis is a variant that spares the typical extensor surfaces and affects intertriginous areas (eg, axillae, inguinal folds, inframammary creases); there is minimal scale. Any portion of the scrotum or penis may be involved. Lesions in the genital region usually do not appear as the distinctly elevated, silvery-scaled plaques typical of psoriasis; instead, they have less scale and are barely raised (or nonraised) and erythematous.

Genital psoriasis can frequently be diagnosed on clinical grounds. Because most patients also have nongenital involvement, a thorough skin examination- particularly of the scalp, elbows, knees, nails, umbilicus, and intergluteal fold-is necessary. If characteristic psoriatic lesions are absent, a skin biopsy may be necessary to confirm the diagnosis.

Low- to mid-potency topical corticosteroids are the mainstay of therapy for genital psoriasis. With long-term topical corticosteroid application, atrophy can occur and may limit the use of these agents in this region of the body. Other options are topical calcipotriol, a vitamin D analogue, or calcineurin inhibitors, such as tacrolimus or pimecrolimus. The latter therapies can be used alone or in combination with topical corticosteroids to minimize adverse effects.

Seborrhea is scalier than this patient's rash. Reiter syndrome is a reactive arthropathy that features painless ulcers. Lichen planus usually presents with purple polygonal papules that are unlike the rash seen here. Trauma was ruled out by the history.