Leprosy, a chronic infectious disease known for many centuries, affects an estimated 1 to 2 million people worldwide. It
occurs mainly in tropical, subtropical, and temperate regions of Southeast Asia, Africa, and South America. In the late 1990s the United States had just under 650 cases, with about 150 new ones diagnosed each year. Most newly diagnosed victims are recent immigrants from Asia and South America. There has been a major effort to eliminate leprosy by the World Health Organization, and this has produced a significant decrease in the number of people who contract the disease.
Cause
Once a disease so dreaded that its victims were isolated in so-called leper colonies, leprosy can now be controlled and its resulting disfigurements prevented. The infectious agent, Mycobacterium leprae, is a bacillus in the same family as the one that causes tuberculosis. (It was discovered in 1874 by a Norwegian physician, Gerhard Hansen, and leprosy is sometimes called Hansen disease.) The agent is thought to be transmitted by skin-to-skin contact and nasal discharges. About 95 percent of the persons exposed to the bacterium are immune, however, so leprosy is not considered highly contagious. Because the bacterium is very slow growing, the incubation period can range from 1 to 30 years, but the average is about 3 to 5 years. The organism invades the peripheral nerves, skin, and mucous membranes, damaging the nerves and causing anesthesia. The resulting insensitivity can lead to unnoticed and therefore neglected injuries; this accounts for many of the deformitiesÑsuch as loss of fingersÑthat occur in leprosy. Paralysis may also result; in advanced cases, numbness of the eyes may lead to blindness through trauma or infection.
Forms of Leprosy
Two main forms of the disease are known:
tuberculoid and
lepromatous. The tuberculoid form mainly involves the skin and nerves. PlaquesÑsuch as a red, raised rim surrounding a pale, flat centerÑoccur most often on the arms and legs. Nerves under the plaques are damaged, and the areas become numb; contraction and wasting of muscles often occur. The lepromatous form is a more generalized infection that involves skin, mouth, nasal passages, upper respiratory tract, eyes, nerves, adrenal glands, and testicles. Various skin eruptions may cover the entire body, but numbness is more patchy and less severe than in tuberculoid leprosy. In advanced stages, however, lepromatous leprosy can cause ulcers, eyebrow loss, collapse of the nose, enlarged earlobes and facial features, and blindness.
Treatment
The main drug used to treat leprosy was dapsone. In the 1960s, however, dapsone-resistant cases began to appear, and today the standard treatment is multi-drug therapy. Dapsone is usually given with other bactericidal drugs such as rifampine and clofazimine, which was approved for U.S. use in 1987 against lepromatous leprosy. Thalidomide, made infamous in the 1960s for its teratogenic effects, has been found to reduce fever, skin lesions, and pain in certain patients and was approved for such use by the U.S. Food and Drug Administration in 1998. Leprosy vaccines, the product of cloning techniques as well as more traditional methods, are being developed and are undergoing clinical trials.