Erythema nodosum leprosum after allergen immunotherapy as initial presentation of lepromatous leprosy treated with novel multidrug regimen.

Although <5% of the world’s population is seemingly susceptible to Mycobacterium leprae infection, host genetics and environmental factors, including immunodeficient or immunosuppressed states, predispose toward the severe disease spectral state of the lepromatous (multibacillary) leprosy.1 We present a case of a patient undergoing allergen immunotherapy, who suddenly developed erythema nodosum leprosum (ENL) as the initial manifestation of lepromatous leprosy (LL) and was treated with a novel monthly multidrug antibiotic regimen in combination with immunomodulatory therapy. This is a rare case report of a difficult-to-treat leprosy immune reaction that developed after a preceding immunologic event of allergen immunotherapy.