[Study of erythema nodosum leprosum].

Erythema nodosum leprosum usually occurs after specific treatment of lepromatous disease or borderline leprosy but may be observed in patients who have not been treated. It is an immune complex vasculitis. Since it is extremely difficult to identify the histological features and the bacteriological study is often negative, this diagnosis relies on clinical examination. Although many authors emphasize the role of reaction to dapsone, there is no one cause of erythema nodosum leprosum which may be triggered by infections, drugs, treatment errors and stress. As a rational treatment of erythema nodosum leprosum may be quite difficult, the clinician must determine the bacteriological and morphological indexes. Anti-inflammatory and anti-allergic treatment should be used before specific drug therapy which should be started after the acute episode triggering the reaction. Finally long-term follow-up of erythema nodosum leprosum is required to avoid recurrence.