[Erythema nodosum: epidemiology, etiology, pathogenesis, clinical picture and therapy].

Erythema Nodosum (EN) is a painful nodular syndrome, most likely of immunologic origin, which involves dermis and subcutaneous tissue. Pathologic process is that of vasculitis of the small veins with inflammation of the septa of the fat lobules (septal panniculitis). It is generally agreed that EN represents a hypersensitive reaction to a variety of antigenic stimuli and thus may be observed in the course of several diseases (infections, immunopathies, malignancies) as well as during drug therapy (with halides, sulfonamides, oral contraceptives). In approximately 50 per cent of the cases an underlying etiology is not apparent (idiopathic form). The clinical picture is always that of a nonspecific systemic illness with low-grade fever (in 60%), malaise (in 67%), arthralgias (in 64%) and arthritis (in 31%), while when there is an associated illness, this may dominate the presentation. Laboratory tests show no specific abnormalities except for those related to an underlying disease. Treatment of idiopathic form includes nonsteroidal antiinflammatory agents which usually ease the discomfort. Steroids, although highly effective, are not recommended because of the benign nature of EN and the danger of disseminating an underlying disease.