What is Mycobacterium Leprae?

Mycobacterium leprae is the bacteria responsible for the disease leprosy, also called Hansen's disease, after Dr. Gerhard Armauer Hansen, the man who discovered the bacteria in 1873. Leprosy is a disease that causes damage to the peripheral nerves and the skin, and can lead to serious complications, including loss of toes and fingers, infertility, and blindness. Scientists do not completely understand how mycobacterium leprae spreads, but they suspect it spreads through respiratory transmission. Though mycobacterium leprae has been widely feared throughout history, modern treatments have been largely successful in treating it.

Mycobacterium leprae is a gram positive, aerobic bacteria that is rod-shaped in appearance. It has the same shape and size as the related bacteria mycobacterium tuberculosis, the bacteria that causes tuberculosis. M. leprae has been cultured in the footpads of armadillos and mice, two of the animals believed responsible for its spread. It has never been grown under artificial conditions.

This bacteria affects the mucous membranes, peripheral nerves and skin. About 10 to 29 percent of those who are exposed to mycobacterium leprae may develop indeterminate, or tuberculoid, leprosy, which is the less severe form of the disease. About 50 percent of those who develop indeterminate leprosy are at risk for succumbing to full-blown, or lepratomous, leprosy, the more severe form of the disease.

Initial symptoms of tuberculoid leprosy include a red, patchy rash on the extremities and torso. Patients may lose some of their touch sensation in the area. Later symptoms can include weakness of the feet or hands, dryness and stiffness of skin, severe pain, vision problems, and enlargement of the nerves surrounding the knees and elbows. Blindness and loss of digits can occur.

Lepratomous leprosy often causes a symmetrical rash on the buttocks, ears, face, knees, elbows and wrists. The rash can have varying characteristics. It may be pale in color or dark, limited or expansive, smooth or elevated above the skin's surface. Additional symptoms can include thickening of facial skin, thinning of eyelashes and eyebrows, lymph node swelling and gynecomastia. Leprosy can cause infertility in males, and can lead to the loss of toes or fingers, loss of vision, or an increased risk of arthritis.

Though much feared historically, leprosy can be cured today. Mycobacterium leprae is considered a highly drug-resistant bacteria, and doctors typically prescribe a combination of antibiotics to eliminate it from the body. Clofazimine, rifampin, and dapsone are most widely used in combination to treat leprosy. Patients must generally follow an antibiotic course for at least one year to treat tuberculoid leprosy, and for at least two years to treat lepratomous leprosy.