Erythema Nodosum Leprosum in a Patient with Borderline Lepromatous Leprosy: A Case Report.

Background: Leprosy, caused by Mycobacterium leprae, presents on a spectrum ranging from tuberculoid to lepromatous disease. Borderline lepromatous leprosy represents an unstable immunological state that predisposes patients to immune-mediated reactions, including erythema nodosum leprosum (ENL), a severe inflammatory complication.

Case presentation: We report a case of a 62-year-old female with borderline lepromatous leprosy who presented with recurrent facial cellulitis and later developed disseminated ENL. She was initially diagnosed following a series of facial infections and confirmatory skin biopsy. Months later, she developed systemic inflammatory lesions consistent with ENL, requiring hospitalization. She was treated with high-dose corticosteroids for ENL and methotrexate to treat type 1 reaction and continued multidrug therapy (MDT) with minocycline, rifampin, and clarithromycin for leprosy, which led to significant clinical improvement.

Conclusion: This case highlights the diagnostic challenges of leprosy in the United States and the importance of recognizing ENL as a severe immunologic complication requiring prompt intervention. A multidisciplinary approach is essential for optimal patient outcomes.