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Leprosy: An Ancient Disease That Continues to Linger

Though there are antibiotics to counter its effects, we haven't eradicated Hansen's Disease, which is why it's so disconcerting that few physicians are able to identify—and thus treat—the condition.
Skin biopsy reveals a nerve infiltrated by Mycobacterium leprae (red-staining) bacteria. (PHOTO: CDC'S PUBLIC HEALTH IMAGE LIBRARY)

Skin biopsy reveals a nerve infiltrated by Mycobacterium leprae (red-staining) bacteria. (PHOTO: CDC'S PUBLIC HEALTH IMAGE LIBRARY)

For most of us, leprosy is an illness unknown. The bible touches on it. It was familiar to ancients in the near East, North Africa, China, and India. Modern texts refer to it as Hansen’s Disease. A recent piece in Harper’s magazine calls it the Separating Sickness.

Leprosy is a rare, infectious disease caused by Mycobacterium leprae. A Norwegian physician, Dr. Gerhard A. Hansen, discovered the bacterial culprit back in 1873. The organism, most common in tropical climates, grows slowly and tends to take hold in relatively cold human body parts: the skin, hands and feet, testicles, the face. Antibiotics to counter M. leprae have been around for decades, but stigma, combined with failure by physicians to identify the condition—about which few are knowledgeable—delays prompt and effective treatment.

“It’s a sensitive issue,” said Dr. Maria Ochoa, director of the Hansen’s Disease Clinic at the Los Angeles County Hospital. “People are hesitant to get treatment because they’re afraid.”

The World Health Organization reports approximately 200,000 new cases each year. The numbers have fallen markedly since 1990, when the agency pushed antibiotic regimens in a global effort to eradicate the disease, but pockets of leprosy persist in Central and South America, Africa, Southeast Asia, and the western Pacific, including the Philippines and Indonesia. Experts point to the difficulty of testing and limited reporting from some regions. The chronic ailment remains a leading cause of infectious and preventable disability.

Years ago, most people with leprosy in the U.S. were forced to live in separate communities. Even if they were permitted to leave after treatment, many chose not to do so.

The incidence of leprosy in the U.S. is tiny. New cases range between 100 and 300 in recent years, with most occurring in the southeast. It may be acquired from armadillos, the only known non-human reservoir for M. leprae. Doctors emphasize that most people exposed, including health care workers, don’t pick up the disease, and patients are no longer contagious upon starting antibiotics.

The disease goes under the radar, says Dr. William Levis, a dermatologist who heads the Hansen's Disease clinic at Bellevue Hospital. The New York registry follows over 400 patients during and after treatment. Most are immigrants. “But you can get it here in the northeast,” said Levis, who, with colleagues, has published on leprosy cases in residents of New York who never left the country.

Leprosy commonly affects the skin “but there’s no typical rash,” according to Levis. In some patients, the immune system responds in a way that creates bulging deformities of fingers, toes, nose, and ears. The face can change, insidiously, leading to a characteristic lion-like appearance. Infiltration of nerves by bacteria leads to gradual loss of sensation and debility. Some patients lose the capacity to blink; this results in eye damage and, in extreme cases, blindness.

“The diagnosis can be tricky,” Levis said. “Most doctors here aren’t familiar with the disease. I’ve seen cases that were missed, even after a skin biopsy.” Several of his patients were previously diagnosed with lupus or another autoimmune condition. “They got treatment for the wrong disease, and then it was too late,” he said.

One problem that contributes to under-reporting is the lack of a reliable detection method for leprosy. The usual test for this group of bacteria, an acid fast stain, doesn’t pick up M. leprae.

At the Infectious Disease Research Institute in Seattle, researchers have developed an assay to rapidly screen for M. leprae. The test measures antibodies to the leprosy-causing bacteria. “You just need a drop of blood,” said Malcolm Duthie, a scientist involved with the project. “It’s simple, like a pregnancy test.” His group is working with a Brazilian company, OrangeLife. So far they’ve used several thousand kits. As things stand, clinicians checking for leprosy have difficulty in diagnosing the disease and generally send samples to a central laboratory.

“We’re working on a smartphone app,” Duthie said. The idea is that doctors and nurses working anywhere could transmit test results and images for confirmation. Recently, the Seattle institute has initiated trials in the Philippines.

Levis is encouraged about the OrangeLife assay and others in development. “We need a test to detect leprosy at an early stage, so that people get prompt treatment and don’t pass it to others,” he said.

Years ago, most people with leprosy in the U.S. were forced to live in separate communities. Even if they were permitted to leave after treatment, many chose not to do so. Two of the most famous and longstanding colonies, in Carville, Louisiana, and Kalaupapa, Hawaii, offered patients a degree of acceptance—in addition to amenities and health care—they couldn’t find elsewhere. It was several decades after the advent of antibiotics before their populations dwindled. Now, leprosy is managed as a treatable, outpatient condition.

Where Ochoa works in Los Angeles, the registry numbers some 380 patients, including people from Mexico and other regions of Central and South America. Others come from India, the Philippines, Vietnam, and Micronesia. The service’s work includes checking patients’ relatives. They’re reluctant to tell their families because they fear rejection, she said. “Some live all their lives with the secret. They don’t want to tell anyone.”

“Usually it’s just a matter of educating the patients,” Ochoa said. They need reassurance that most people don’t get leprosy, even if they’re exposed.

Doctors need more education too, she suggests. “Leprosy is not just a skin disease,” Ochoa said. “It should be part of the medical school curriculum here and everywhere.” They need to know it still exists. “Patients go from doctor to doctor. Some get false positive results for autoimmune conditions or syphilis. They get treated for those, incorrectly, and then go years without the right diagnosis.” And the delays lead to disability. “Nerve damage leads to loss of feeling in the patients’ arms and legs. Then they get injuries. What follows are deformities,” Ochoa said.

“The most important thing is to get over the stigma,” Ochoa said. “You can treat patients much more effectively if they come in early.”