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- Patient Comments: Leprosy - Symptoms
- Patient Comments: Leprosy - Risk Factors
- Leprosy (Hansen's disease) facts
- What is leprosy?
- What is the history of leprosy (Hansen's disease)?
- What causes leprosy?
- What are the risk factors for leprosy?
- What are leprosy early symptoms and signs?
- Are there different forms (classifications) of leprosy?
- How is leprosy transmitted? Is leprosy contagious?
- How do doctors diagnose leprosy?
- What specialists treat leprosy?
- What is the treatment for leprosy?
- What are the complications of leprosy?
- Is it possible to prevent leprosy?
- What is the prognosis of leprosy?
- Where can I find more information on leprosy?
What causes leprosy?
Leprosy is caused mainly by Mycobacterium leprae, a rod-shaped bacillus that is an obligate intracellular (only grows inside of certain human and animal cells) bacterium. M. leprae is termed an "acid fast" bacterium because of its chemical characteristics. When special stains are used for microscopic analysis, it stains red on a blue background due to mycolic acid content in its cell walls. The Ziehl-Neelsen stain is an example of the special staining techniques used to view the acid-fast organisms under the microscope.
Currently, the organisms cannot be cultured on artificial media. The bacteria take an extremely long time to reproduce inside of cells (about 12-14 days as compared to minutes to hours for most bacteria). The bacteria grow best at 80.9 F-86 F, so cooler areas of the body tend to develop the infection. The bacteria grow very well in the body's macrophages (a type of immune system cell) and Schwann cells (cells that cover and protect nerve axons). M. leprae is genetically related to M. tuberculosis (the type of bacteria that cause tuberculosis) and other mycobacteria that infect humans. As with malaria, patients with leprosy produce anti-endothelial antibodies (antibodies against the lining tissues of blood vessels), but the role of these antibodies in these diseases is still under investigation.
In 2009, investigators discovered a new Mycobacterium species, M. lepromatosis, which causes diffuse disease (lepromatous leprosy). This new species (determined by genetic analysis) was found in patients located in Mexico and the Caribbean islands.
What are the risk factors for leprosy?
People at highest risk are those who live in the areas where leprosy is endemic (parts of India, China, Japan, Nepal, Egypt, and other areas) and especially those people in constant physical contact with infected people. In addition, there is some evidence that genetic defects in the immune system may cause certain people to be more likely to become infected (region q25 on chromosome 6). Additionally, people who handle certain animals that are known to carry the bacteria (for example, armadillos, African chimpanzee, sooty mangabey, and cynomolgus macaque) are at risk of getting the bacteria from the animals, especially if they do not wear gloves while handling the animals.