An asymptomatic, circular, scaling lesion on the trunk of a 42-year-old man consistently reappears after clearing. The lesion initially erupted 3 months earlier; since then, it has arisen, lasted a few weeks, and disappeared several times. The patient has no other complaints; he takes no medications.
The presentation strongly suggested erythema annulare centrifugum, a reactive process to an underlying disease that is often undiagnosed. Tinea corporis, tinea versicolor, and granuloma annulare lesions do not wax and wane as did this patient’s eruption. The rash of lupus erythematosus also tends to persist and typically arises on sun-exposed skin. Perform a potassium hydroxide examination, for a dermatophyte infection, which is the most common underlying disorder; this patient had tinea pedis. Further workup is needed only if the patient has symptoms other than the rash. Treatment of the tinea pedis resulted in resolution of the infection and the erythema annulare centrifugum as well.