What is the pathogenesis of erythema nodosum?

Erythema nodosum is usually considered to represent a delayed hypersensitivity response that reflects a common reaction pattern to a wide variety of eliciting factors. The subcutaneous septa in well-developed lesions often contain granulomas, and recent work has shown a strong correlation between genetic polymorphisms of tumor necrosis factor–a and erythema nodosum (TNF-a promotes granuloma formation). Reactive oxygen intermediates may be involved in the tissue damage and inflammation that accompany erythema nodosum.

Labunski S, Posern G, Ludwig S, et al: Tumor necrosis factor-alpha promoter polymorphism in erythema nodosum, Acta Derm Venereol 81:18–21, 2001.