BACKGROUND Lucio's phenomenon, also called necrotizing erythema, is a rare acute manifestation which sometimes introduces diffuse lepromatous leprosy, almost exclusively in Central American populations. METHODS A 76-year-old polynesian man of chinese ethnic origin had necrotizing erythema for several months before development of Lucio's leprosy. The patient had necrotizing lesions of the lower limbs with large polygonal scars and poor general health status. Diagnosis was based on the discovery of acid-fast bacilli at the pathology examination of skin biopsies. The necrotizing zones appeared as cutaneous vasculitis with angiogenesis of the superficial dermis and presence of Hansen bacilli within the endothelium. CONCLUSIONS This case of diffuse lepromatous leprosy, the first reported in the South Pacific, emphasizes the polymorphism of leprosy and the importance of recognizing rare clinical forms, especially in the tropics. Anti-Hansen drugs are effective.