Erythema nodosum leprosum in Singapore

Erythema Nodosum Leprosum (ENL) or Type II reaction is an immune complex syndrome seen in multibacillary leprosy. 20 patients with histological confirmation of ENL in leprosy were studied from 1982 to 1986. These patients had a range of clinical signs, from fever, tender dusky nodules, bullae, ulcers to lymphadenopathy, arthralgia and neuritis. The four major histological patterns are: a) classical pattern showing heavy infiltrations of neutrophils in three cases, b) sub-epidermal bulla pattern with marked oedema of the upper dermis, and collections of neutrophils in five cases, c) vasculitis pattern, affecting superficial and mid-dermal vessels, leading to epidermal necrosis, bulla formation and ulceration. Dilated vessels, congestion, lumenal fibrin clots and fibrinoid necrosis of vessels were seen, d) non-specific picture in nine cases with mild oedema, infiltration with neutrophils, and two cases with minimal reaction had chronic ENL with clinical vasculitis. All the five cases with vasculitis showed C1q, C3 and fibrinogen in the vessels. Comparing ENL reactions reported in Asia, our pattern is similar to that of Malaysians with the majority showing sub-epidermal oedema. Vasculitis is more common in India. Oedema with collagen necrosis as seen in acute ENL with iritis in New Guinea. The Lucio's phenomenon was not seen in any of the countries in Asia.