Leprosy is a chronic infectious disease of humans caused by the bacteria Mycobacterium leprae. For many years, it was considered a mysterious disorder associated with some type of curse, and persons with the disease were isolated and ostracized. Today, there is effective treatment and the disease can be cured. There is no longer any justification for isolating persons with leprosy.
The disease can affect the skin, mucous membranes, and eyes and some of the nerves that are located outside the central nervous system (peripheral nerves). These are primarily the nerves of the hands, feet, and eyes, and some of the nerves in the skin. In severe, untreated cases, loss of sensation, muscle paralysis of hands and feet, disfigurement, and blindness may occur.
Leprosy has traditionally been classified into two major types, tuberculoid and lepromatous. Patients with tuberculoid leprosy have limited disease and relatively few bacteria in the skin and nerves, while lepromatous patients have widespread disease and large numbers of bacteria. Tuberculoid leprosy is characterized by a few flat or slightly raised skin lesions of various sizes that are typically pale or slightly red, dry, hairless, and numb to touch (anesthetic). Lepromatous leprosy is at the other end of the spectrum, with a much more generalized disease, diffuse involvement of the skin, thickening of many peripheral nerves, and at times involvement of other organs, such as eyes, nose, testicles, and bone. There are also intermediate subtypes between these two extremes that are commonly known as borderline leprosy. The intermediate subtypes are borderline tuberculoid, midborderline, and borderline lepromatous leprosy. Borderline leprosy and the subtypes are characterized by more extensive disease than polar tuberculoid, with more numerous skin lesions and more nerve involvement, but not as widespread disease as in lepromatous leprosy. Indeterminate leprosy refers to a very early form of leprosy that consists of a single skin lesion with slightly diminished sensation to touch. It will usually progress to one of the major types of leprosy.
In 1982, the World Health Organization proposed a simplified classification that has only two classifications, Paucibacillary (PB) and Multibacillary (MB), leprosy. This classification is now used worldwide for treatment purposes. The older and somewhat more complex classification is still used in some programs, especially for clinical research studies. The Paucibacillary classification encompasses indeterminate, tuberculoid and borderline tuberculoid leprosy. The Multibacillary classification includes midborderline, borderline lepromatous and lepromatous leprosy.
The earliest symptoms are usually skin lesions that are typically flat, pale (hypopigmented) or reddish (erythematous) spots in the skin with slightly decreased sensitivity to touch or pain. These lesions typically do not present with other symptoms, such as burning or pain. There may be some hair loss in the affected area. As the skin lesions progress, they may become raised and, in some cases, nodules may form. The symptoms of nerve involvement include diminished sensation or feeling in the affected areas (anesthesia) and, sometimes, burning and tingling sensations (paresthesias). In more advanced cases, there may be weakness, paralysis, and atrophy of muscle in the hands or feet.
Persons with tuberculoid and borderline tuberculoid leprosy have limited disease with relatively few skin lesions and only a few affected nerves. However, early in the course of the disease, they may have significant sensory loss and muscle weakness, even though only one hand or foot is involved. Persons with lepromatous leprosy may have minimal loss of sensation at the onset; however, if untreated, they will develop extensive involvement of the skin and nerves. The complications that may occur include eye involvement and deformities of the face, hands, and feet. Deformities of the face can result from destruction of the partition in the nose that divides the nostrils (nasal septum) and other facial tissues. In advanced disease, persons with lepromatous leprosy may lose their eyebrows and eyelashes, and the eyelids may become paralyzed so that individuals cannot blink or close their eyes properly. The earlobes may enlarge or become wrinkled. Deformities of the hands and feet may result from muscle paralysis and repeated trauma that is not felt due to sensory loss.
The most serious complication of leprosy is the nerve damage that may occur sometimes even after treatment is begun. Much of the nerve damage occurs during a type of immunologic problem that occurs in 25 to 50% of patients during treatment and is commonly known as a reaction. Reactions are not drug reactions or allergies, but are the patient’s own immune system reacting against the dead bacteria that are still in the skin and nerves. Patients with the intermediate or borderline type of disease may get a type of reaction known as reversal reaction, in which there is redness and swelling of the skin lesions and swelling, tenderness, and pain in the nerves of the hands and feet. During this process, nerve damage can occur.
The second type of reaction occurs only in borderline lepromatous and lepromatous disease, and is known as erythema nodosum leprosum (ENL). This syndrome is characterized by fever and raised, red, painful skin nodules. There may also be pain and tenderness of the nerves with subsequent nerve damage in the hands and feet. ENL may also be associated with joint disease (polyarthralgia), eye inflammation, and inflammation of the testicles.
During reactions and at times without any signs of reaction, there may be damage to the nerves of the face resulting in weakness of closure of the eyelids and loss of feeling in the cornea (corneal anesthesia). This can result in corneal dryness and scarring and lead to blindness. Persons with lepromatous leprosy may also have inflammation of the iris and the sclera of the eye, which can lead to visual impairment and, in some cases, blindness.
Leprosy is a chronic infectious disease of humans caused by the bacteria Mycobacterium leprae. The disease has been known and described for several thousand years in India and China. Over 100 years ago, Armauer Hansen in Norway identified the bacteria as the cause of leprosy.
The way in which the disease is transmitted is not fully understood. The bacteria grow only in living hosts and have not been grown in laboratory media, except in certain kinds of mice, rats, and armadillos. Some wild armadillos also carry the bacteria. The most likely way of spread appears to be through the respiratory tract, since large numbers of bacteria are sometimes found in the noses and mouths of untreated patients. When these are released into the environment, they can be inhaled by other susceptible persons.
Most people have a natural immunity to the disease and will not contract it even if they are exposed to it. Only about 5 percent of all people are susceptible to the disease. More than one-half of new cases give no history of any known contact with a leprosy patient.
Leprosy is relatively rare in the United States but is prevalent in some countries of Asia, Africa, and South America. There are about 7,000 persons in the United States that have been treated for the disease, and from 150-200 new cases are reported annually in the United States. About 85% of the U.S. cases are persons who have immigrated from other countries. North American Indians in the U.S.A. appear to be immune to this disease.
Worldwide, there are about 700,000 new cases reported each year, with about 800,000 cases under treatment in 1998. There are an additional estimated two to three million persons who have residual deformities and disabilities from the disease, even though they have been cured of the infection. Some of the countries with the largest number of cases are India, Brazil, Indonesia, Bangladesh, Myanmar, Nigeria, and Mozambique.
The diagnosis can usually be made by the history and characteristic findings on examination. The important findings are decreased ability to feel light touch in a skin spot, enlarged or tender nerves in the arms or legs, numbness in a hand or foot, and finding the bacteria in the skin. There may also be loss of hair in the affected skin areas. A special type of skin smear is commonly done and will demonstrate the bacteria in the skin in lepromatous and borderline lepromatous cases. The bacteria are too few in tuberculoid cases to be found in a skin smear. A skin biopsy of a lesion can also be helpful to confirm the diagnosis. There are no blood tests or skin tests at the present time that are helpful in the diagnosis.
Leprosy is a treatable and curable disease. The vast majority of patients can take their medication at home and continue their regular work and other activities. Patients with leprosy do not need to be isolated. It is important to note that the drugs used to treat leprosy are very effective in killing the bacteria, and patients on treatment are not infectious and do not spread the disease.
The currently available drugs are very effective, and treatment is much shorter than was common 20 years ago. The major drugs are dapsone, rifampin, and clofazimine. Dapsone and rifampin can be given for six months for patients with PB disease (indeterminate, tuberculoid or borderline tuberculoid disease), and dapsone, rifampin, and clofazimine are given for two years for patients with MB disease (midborderline, borderline lepromatous and lepromatous disease). Even shorter regimens using the above drugs are being developed, and used in some parts of the world, and in some areas patients with only one skin lesion are treated with only a single dose of medication. Several other drugs, minocycline, oflaxacin, and clarithromycin, have also been found effective for treatment and are used in cases in which there are allergies or intolerance to the three commonly used drugs.
Patients with mild reactions, as described above, can be treated symptomatically with analgesics, but most cases will also require prednisone or similar drugs for control of the reactions. These may need to be given for many months at times. The drug thalidomide (Thalomid) has been approved by the FDA as a treatment for erythema nodosum leprosum (ENL), an inflammatory complication sometimes associated with leprosy that results in painful skin lesions. It is not effective in reversal reaction and does not kill bacteria. Thalidomide can have severe effects on a developing fetus and must be administered with extreme caution. It cannot generally be given to women of childbearing potential.
Ocular complications of erythema nodosum leprosum (ENL) must be treated promptly to prevent permanent damage to the eyes. Local atropine and hydrocortisone eye drops may be used to keep the pupils dilated and reduce the inflammation until the reaction subsides. Patients with corneal dryness are treated with eye drops and substitutes for the eye's natural lubricants.
Leprosy can be cured, and most disabilities and deformities can be prevented. Contrary to common perceptions, leprosy does not cause fingers and toes to drop off. The loss of fingers and toes that is sometimes seen is not due to the leprosy infection but to injuries that occur because of nerve damage and loss of feeling in the extremities. These injuries may become secondarily infected with other kinds of bacteria and cause the toes or fingers to lose infected bone and ultimately shorten. If the injuries can be prevented, much of the disability will not occur. The most important thing that can be done to prevent permanent disability is to diagnose and treat patients at the very earliest stages of the disease. They need to be started on appropriate drugs to kill the bacteria, and reactions must be treated promptly if they occur. For those who already have had some nerve damage, health education in the care of hands, feet, and eyes is very important to prevent further injury and deformity.
Some people with leprosy may benefit from special shoes that compensate for loss of sensation in the feet. Gloves or special tools can be used to prevent injury to hands that have lost sensation. Surgery may be necessary to treat eye problems or correct certain deformities of the hands and feet. The goal of surgery is to improve function and the quality of life.
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