Erythema marginatum in rheumatic fever: early diagnosis by skin biopsy.

Skin biopsy of a 10-year-old boy with a 3-week history of recurrent rash and fever demonstrated histologic changes suggesting a diagnosis of erythema marginatum associated with rheumatic fever. Subsequently, the patient developed classic cardiac and arthritic manifestations. Skin biopsy is recommended for the early diagnosis of rheumatic fever.