A 58-year-old man from Florida showed up to a clinic complaining about a strange mark on his arm. The lesion had been growing over the course of five months, and causing him occasional sharp pain. He was also experiencing decreased sensation in the reddened area. 

Previously, he had been admitted to an urgent care center and tested for Lyme disease, which came back negative. He was given antihistamines for his skin irritation and sent home, but returned months later when the inflammation became worse, doctors have reported in a new case study published in BMJ Case Reports.

The doctors were unsure what could be causing the man's lesion. He was a self-proclaimed out-doors person, which widened the possibilities somewhat, with doctors suggested everything from toxoplasmosis to a deep fungal infection as possible causes.

In an attempt to widen the field of possibilities, the doctors explored further back into the man's past and discovered he had been an armadillo hunter some 30 years prior. In this job – for scientific research purposes – he would trap and sell armadillos to researchers. This opened up the possibility that he could have leprosy.

Leprosy – also known as Hansen's disease – is not common in the US, with around 200 cases per year. Most cases worldwide are transmitted through close contact with those infected or by breathing in airborne bacteria, or getting it in wounds or damaged skin. In the US, the authors write, the majority of cases (60-75 percent) occur in immigrants and those who have had close contact with them, especially those from the Federated States of Micronesia or Marshall Islands. However, the largest number of new cases in the Gulf Coast states over the last 20 years is likely due to zoonotic transmissions from armadillos.

"In the southern USA, M. leprae can be spread by armadillos shedding the bacilli into the environment through their bodily secretions. The bacteria are able to survive up to 8 months in the environment," the doctors wrote in the case report.

"Leprosy infection is difficult to diagnose due to its long incubation period of 8–12 years and lack of a diagnostic test able to identify infection before clinical symptoms present."

After numerous tests and consultation with experts at the National Hansens Center, the patient was diagnosed with leprosy, treated with a course of several antibiotics, and will likely recover fully. Following up after five months, the lesion had shrunk and sensation was returning to the man's arm.