Erythema Nodosum Leprosum Triggered by Herpes Simplex Infection: A Case Report.

Leprosy, caused by Mycobacterium leprae, is a chronic granulomatous disease primarily affecting the skin and peripheral nerves. Erythema nodosum leprosum (ENL), or type 2 lepra reaction, is an immunologic complication of lepromatous leprosy, often presenting with erythematous nodules, fever, and systemic inflammation. Early recognition is crucial to prevent chronic complications. We report a 44-year-old man who developed facial erythematous nodules and fever following a sore throat, initially suggestive of a drug eruption or viral infection. Laboratory tests revealed neutrophilia, elevated inflammatory markers, mild transaminitis, and positive herpes simplex virus IgM. Imaging showed right periorbital soft tissue thickening. Skin biopsy confirmed lepromatous leprosy, and the rash was identified as ENL, likely triggered by acute herpes simplex virus infection. The patient received antibiotics followed by anti-leprosy therapy (dapsone, clofazimine, rifampicin) and tapering corticosteroids, with complete resolution of symptoms. This case highlights the importance of considering leprosy and its immunologic reactions in acute facial eruptions.