Erythema nodosum leprosum (ENL) with sub-acute mono-neuritis multiplex: A rare presentation and challenging disease to manage

Hansen’s disease (HD), a chronic granulomatous infection caused by Mycobacterium leprae with a wide clinical spectrum dependent on the host’s immune response. HD is rare in Australia, often clinically polymorphic with immune-mediated skin and nerve pathology frequently confusing the clinical picture. We report a case of lepromatous leprosy in a 37-year-old Aboriginal man with necrotic erythema nodosum leprosum (ENL), with a sub-acute progressive mononeuritis multiplex. Clinically, he had widespread polymorphic skin lesions, severe oral ulceration and decreased sensation in both feet and left hand. Other clinical features of leprosy included: bilateral anterior uveitis and asymmetrical ear lobe thickening. There were scattered tender subcutaneous nodules covered by crusted ulcers and infiltrative erythematous dermal plaques with central eschars, involving his face, abdomen, arms and thighs. Anaesthetic trophic skin changes with multiple tender, thickened peripheral nerves. Left ulnar and median nerve motor weakness. Histopathology demonstrated lymphohistiocytic inflammatory dermal infiltrate, with associated granuloma formation, accompanying acute inflammation and widespread ulceration. Split skin smears were positive for M. leprae. Clinically his skin lesions and neurology improved after six weeks therapy; with a combination of rifampicin, clofazimine and dapsone, as per WHO Guidelines. Adjunctive steroids were prescribed for his ENL. Although leprosy is rare, inclusion in the differential diagnosis remains important for immigrants from endemic countries and indigenous patients in Australia. ENL can be a presenting feature of leprosy; further complicating leprosy diagnosis. Aggressive systemic immune-modulation is required to reduce patient morbidity from flares of ENL that typically follow initiation of anti-leprotic therapy.

Dr. Francis Yap

Royal Perth Hospital