Abstract

Leprosy in the United States is rare, 159 new cases were reported in the U.S. in 2020. Leprosy is caused by acid-fast bacteria called "Mycobacterium leprae complex,” includes Mycobacterium leprae and Mycobacterium lepromatosis. The incubation period is usually 3 - 5 years, and it may take up to 20 years to develop signs of the infection, which often makes it very difficult to trace the source of infection. In the southern US, some armadillos are naturally infected, and handling those animals can cause spread to humans. Our patient is a young male in his 30s, presenting with bumps all over the body for a few months with no recent travel history. Routine blood tests, QuantiFERON, RPR, and autoantibodies panel were negative. A skin biopsy of the lesion showed a diffuse infiltrate of foamy histiocytes with pink material, lymphocytes, and plasma cells, extending into the reticular dermis. Occasionally, histiocytes were seen wrapping/encircling the nerves. Stains for CD1a, S100, treponema pallidum, and fungus were negative. AFB (Fite) stain showed globi/large groups of acid-fast bacilli within the foamy histiocytes which is consistent with the diagnosis of leprosy. Diagnosis of leprosy is mainly based on clinical suspicion, skin biopsy, and PCR. Some of the skin lesions do not contain identifiable bacteria, and PCR has good specificity but sensitivity varies with the type of leprosy. A multidrug regimen including rifampin, dapsone, and clofazimine is a mainstay treatment. Although leprosy is a rare disease in the U.S., keeping the suspicion high would avoid missing these cases.