Differential diagnosis of annular lesions

Although most annular lesions will be typical of a dermatophytosis, physici ans must consider other possible diagnoses. Tinea corporis can often be dia gnosed on the basis of a positive potassium hydroxide examination, Topical and systemic antifungals are usually curative, Pityriasis rosea is characte rized by small, fawn-colored lesions distributed along skin cleavage lines. Treatment is symptomatic. Granuloma annulare is characterized by nonscaly, annular plaques with indurated borders, typically on the extremities, One half of Eases resolve spontaneously within two years. Sarcoidosis can prese nt as annular, indurated plaques similar in appearance to the lesions of gr anuloma annulare. Diagnosis is based on histopathology and the involvement of other organ systems. Hansen's disease can mimic tinea corporis by presen ting as one or more annular, sometimes scaly. plaques. Urticaria may affect 10 to 20 percent of the population. The annular plaques lack scale and are evanescent. Subacute cutaneous lupus erythematosus can present in an annul ar form on sun-exposed surfaces or in a papulosquamous form. Erythema annul are centrifugum typically presents as annular patches with trailing scale i nside erythematous borders.