Erythema Nodosum

Erythema nodosum (EN) is a common acute nodular septal panniculitis, characterized by the sudden onset of erythematous, firm, solid, deep nodules or plaques painful on palpation and mainly localized on extensor surfaces of the legs. These nodules are characterized by a typical histological appearance regardless of the etiology, marked by acute inflammation of the dermo-hypodermic junction and interlobular septa of the hypodermic fat, evolving without necrosis or sequelae. Erythema nodosum is an acute or recurrent hypersensitivity reaction to a variety of antigens with a clear female predominance that may be associated with several different stimuli or pathological conditions. See  Erythema Nodosum.