[Review: update on erythema nodosum leprosum].

Erythema nodosum leprosum (ENL) is an immunological reaction corresponding to vascularitis due to circulating immune complexes usually occurring during treatment of lepromatous leprosy. The precise mechanism underlying ENL are unclear but involvement of tumor necrosis factor alpha (TNFalpha) is suspected. Based on this suspicion pentoxifylline has been used instead of conventional treatments such as corticosteroids and thalidomide.