Erythema nodosum

Abstract

Erythema nodosum (EN) is typically characterized by suddenly symmetrically appearing deep painful red nodules on the pretibial area. It rarely recurs, but in some cases it becomes chronic. Histopathologically EN is a septal panniculitis without vasculitis. EN is probably a hypersensitivity reaction to a known or unknown antigen. A physician diagnosing EN always has to consider it as a secondary disease. The most common underlying causes are infections (especially streptococcal), inflammatory bowel diseases, sarcoidosis, and drugs, and it can also be idiopathic. After ruling out erysipelas/cellulitis, thrombophlebitis, insect bite, or urticaria, other panniculitides and vasculitides have to be considered in differential diagnoses. It is self-limited; therefore, the therapy is often only symptomatic besides eliminating or treating aggravating causes. Physical pain relief methods (bed rest and cooling the inflamed skin) are the bases of symptomatic care. EN quickly responds to systemic steroid, but in most cases its use is neither recommended nor necessary. Systemic therapeutic options consist mainly of nonsteroidal anti-inflammatory drugs; in unresponsive cases, potassium iodine, colchicine, dapsone, hydroxychloroquine, thalidomide, TNF alpha inhibitors, and rarely other immunosuppressant and chemotherapeutic agents are the therapeutic options. EN usually resolves without any remaining sign. From the treatment choices, physicians should choose the best according to the possible or proven underlying/aggravating agent and also consider that most of the drugs recommended based on case reports and personal experiences are off-label.