HIV patient tested positive for the bacterium that causes leprosy.

Ohio doctors report they got a diagnostic surprise when an HIV patient tested positive for the bacterium that causesleprosy.

What was even more surprising was that the initial infection most likely occurred decades earlier, from exposure to an armadillo.

Soon after starting treatment for the HIV infection, the Ohio man developed lesions on his skin that didn't respond to antibiotic treatment. His doctors eventually confirmed that the lesions were caused by Mycobacterium leprae bacteria, an infection more commonly known as leprosy.

"With the way he presented, typically, any clinician would think of an infection with bacteria, and that's what we were thinking, but he was not responding to regular antibiotic treatment," said Dr. Madhuri Sopirala, the lead author of a letter on the unusual case in the Oct. 20 issue of theNew England Journal of Medicine.

And, it was his failure to respond to antibiotic treatment that prompted his physicians to look for less common reasons for the man's condition.

Leprosy, which is also called Hansen's disease, is quite uncommon in the United States. In 2008, the last year for which statistics are available, just 150 people contracted Hansen's disease in the United States, according to the National Hansen's Disease Program. The majority of these cases occurred in California, Florida, Hawaii, Louisiana, Massachusetts, New York and Texas.

The main symptom of the disease is skin lesions that may be raised or flat, light-colored or pigmented, and there may be no feeling within the skin lesion. The disease can only be diagnosed through a skin biopsy, and long-term treatment with antibiotics is effective when started early.

People who live in Texas or Louisiana are more likely to contract Hansen's disease, as are people who've traveled to parts of the world where leprosy is still common.

In April, Hansen's disease experts added armadillo exposure to the list of possible risk factors, cautioning that people should stay away from armadillos.

In the case of the Ohio man, however, he hadn't been around armadillos since he was a teenager. He was 41 when he was diagnosed with Hansen's disease. He had never traveled outside of the United States, and said he hadn't been around anyone who had lived in areas where leprosy was still common. He had lived in Ohio all of his adult life, but had grown up in Mississippi, where he hunted armadillos as a teenager and touched their carcasses.

"The long duration of incubation is not a surprise to people who deal with this disease -- 20 years' incubation is not outside of our experience," said Dr. David Scollard, chief of the clinical branch and a pathologist at the National Hansen's Disease Program. "And, we have certainly seen this turn up as an opportunistic infection in people who are immunosuppressed: people with HIV, people who have had heart or kidney transplants, people receiving chemotherapy, [and people on certain medications that dampen the immune system response]. The biggest problem we have is that most clinicians don't think of it."

Sopirala, who is with the Ohio State University Medical Center in Columbus, said that if someone has symptoms consistent with leprosy, such as skin lesions that have no feeling of pain, and the symptoms don't improve with antibiotic treatment, leprosy should be considered as a possible diagnosis, especially if someone lives or has lived in an area of the southern United States where armadillo exposure is a possibility.

"This was a nice piece of detective work," Dr. Richard Truman said of the study. "Leprosy remains a very rare disease, but it's another one of the diseases that should be considered with chronic [skin] lesions that don't respond to treatment," he said. Truman is a research scientist from the National Hansen's Disease Program at Louisiana State University in Baton Rouge.

More information

Learn more about leprosy from the National Hansen's Disease Program.