Erythema nodosum leprosum mimicking Sweet's syndrome: an uncommon presentation.

Erythema nodosum leprosum (ENL) lesions may uncommonly develop ulceration, necrosis, pustulation or bullae. This 60 year-old female was hospitalised with previously undiagnosed multibacillary (BL) leprosy and Sweet's syndrome-like ENL, a presentation that is rarely reported. In addition to skin lesions simulating Sweet's syndrome, she had anaemia, elevated ESR, and a peripheral leucocytosis with neutrophilia, the laboratory features of Sweet's syndrome. The final diagnosis was made from chronic iridocyclitis, presence of lepra bacilli in slit-skin smears, and histology. The pathogenesis of Sweet's-like ENL remains conjectural. In Sweet's syndrome a complex interplay of various cytokines leading to an abundance of pro- inflammatory cytokines in the target tissues has been postulated to initiate an abnormal tissue response to certain antigens; such findings may eventually explain these uncommon lepra reactions as well.