Leprosy in the Heartland

Mycobacterium leprae is an acid fast bacterium that causes leprosy, also known as Hansen's disease. M. leprae spreads primarily through respiratory droplets and skin contact, and widespread migration of the human population may lead to infection in non-endemic areas. Leprosy mainly affects the skin, peripheral nerves, mucosa of the upper respiratory tract, and the eyes, presenting as a spectrum of disease based on the host immune response consisting of skin lesions, areas of anesthesia, local tissue destruction, and even blindness or glomerulonephritis in severe cases.

We describe a case of leprosy presenting in a South Dakota resident. Before this case, leprosy had not been reported in South Dakota in 11 years. The patient presented with chronic skin lesions with areas of anesthesia on her right knee and left elbow. Physical exam was unremarkable aside from the skin lesions, which had areas of decreased sensation over the involved skin. Biopsy of the lesions was positive for noncaseating granulomas with lymphocytic infiltrate that were acid-fast bacillus positive. The biopsy was sent to the National Hansen's Disease Program for further molecular testing, which confirmed M. leprae infection. The patient underwent 12 months of dapsone 100 mg po qd and rifampin 600 mg po qd per U.S. guidelines from the National Hansen's Disease Program Clinical Center. The patient responded well to treatment until developing a reversal reaction after nine months, which was resolved with corticosteroid treatment. Both dermatology and infectious disease continue to follow the patient, and she continues to do well with no evidence of recurrence of active infection or evidence of reversal reaction.

It is important that clinicians be aware of the possibility of uncommon presentations/diseases such as leprosy in areas where it is extremely rare (such as South Dakota) due to immigration and travel among patients. The rarity of leprosy in areas like South Dakota, in addition to its potential for misdiagnosis, may lead to delay of treatment in the patient. Delays in treatment can allow progression of the disease causing skin lesions and possible nerve damage.