Tinea cruris is a dermatophytosis that is commonly caused by Trichophyton rubrum or T. mentagrophytes. The primary risk factors are associated with a moist environment (ie, warm weather, wet and restrictive clothing, obesity causing constant apposition of skinfolds). Men are affected more than women because of apposition of the scrotum and thigh.
Typically, a pruritic, ringed lesion extends from the crural fold over the adjacent upper inner thigh. Infection may be bilateral. Lesions may be complicated by maceration, miliaria, secondary bacterial or candidal infection, and reactions to treatment. In addition, scratch dermatitis and lichenification can occur. Recurrence is common because fungi may repeatedly infect susceptible people or people with onychomycosis or tinea pedis, which can serve as a dermatophyte reservoir. Flare-ups occur more often during summer.
Scrotal involvement is usually absent or slight; by contrast, the scrotum is often inflamed in candidal intertrigo or lichen simplex chronicus. If the appearance is not diagnostic, a potassium hydroxide wet mount is helpful.
Differential diagnosis of tinea cruris includes
(See table: Options for Treatment of Superficial Fungal Infections*.)
Antifungal choices include terbinafine, miconazole, clotrimazole, ketoconazole, econazole, naftifine, and (uncommonly) ciclopirox applied 2 times a day for 10 to 14 days.
Itraconazole 200 mg orally once a day or terbinafine 250 mg orally once a day for 3 to 6 weeks may be needed in patients who have refractory, inflammatory, or widespread infections.