Tinea incognito due to Trichophyton rubrum--a case report.

Tinea incognito is a dermatophyte infection modified by inappropriate and often prolonged use of topical steroids. We present a case of tinea incognito in a 72-year-old woman, referred by her family physician who had unsuccessfully treated the lesions for 3 weeks with topical steroid cream. Physical examination revealed multiple nummular scaly papules and plaques which spread over her arms and trunk. The lesions were circular, erythematous, sharply demarcated with raised scaly edge some coalescing to form moderately infiltrated areas. Direct microscopy was positive for fungal hyphae. Fungal culture on Sabouraud's agar grew Trichophyton rubrum. The patient was successfully treated with oral terbinafine 250 mg daily and 1% clotrimazole cream twice daily. The present case highlights the importance of considering a dermatophytosis when clinical presentation of dermatosis is atypical. Disseminated scaly infiltrate lesions should be investigated for fungal infection in patients previously treated with steroids, as to avoid misdiagnosis and spread of infection.