Beware the Armadillo! A Case of Erythema Nodosum Leprosum

The good Dr. Mannion, on his last Monday of residency ever, presented a scintillating case of a young Micronesian woman with chronic skin rash & unclear history of leprosy who was admitted with recurrent fever, headache, and transient shock, found to have erythema nodosum leprosum.

Let’s start with a refresher on leprosy.

  • A chronic infection caused by Mycobacterium leprae and Mycobacterium lepromatosis, leprosy classically affects the skin and peripheral nerves, and can result in severe disfigurement & disability.
  • Contrary to popular belief, it is NOT highly contagious, but was viewed as a curse in the Middle Ages, leading to the formation of leper colonies, or leprosariums.
  • M. leprae is enzootic in the nine-banded armadillo, although the mechanism of transmission from armadillos to humans is unknown.
  • Diagnosis is established by AFB staining on skin/cutaneous nerve biopsies.
  • Treatment with multidrug regimens is highly effective, and varies depending on the class of leprosy. There are 5 classes, ranging from tuberculoid (paucibacillary) to lepromatous (multibacillary) disease.
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In ~30-50% of cases, immunologic reactions can occur, causing a Type I (reversal reaction) or Type 2 (erythema nodosum leprosum or ENL) reaction. Outside of this phenomenon, leprosy is not often thought to cause systemic illness. ENL presents as a sudden eruption of numerous painful nodules, along with fever, headache, and malaise. It can be confused for meningitis, as it was in this patient. It typically lasts 1-2 weeks, and is recurrent unless proper treatment is administered. High-dose prednisone is typically recommended, with thalidomide a solid alternative (though contraindicated in our patient who was of childbearing age.)

 ENL Skin Lesions, courtesy of Kahawita et al. April 2008. Transactions of the Royal Society of Tropical Medicine. 

ENL Skin Lesions, courtesy of Kahawita et al. April 2008. Transactions of the Royal Society of Tropical Medicine.