The differential diagnosis of erythema nodosum.

Erythema nodosum is an uncommonly seen skin eruption which may be a marker of underlying systemic or infectious disease. It may also occur as a reaction to a variety of medications. The diagnosis of erythema nodosum should prompt a thorough investigation of possible causes or associated conditions which may be treatable. This paper presents a case of erythema nodosum and reviews the differential diagnosis of its causes and of similar appearing skin lesions.