Father Damien was a Roman Catholic missionary who helped lepers on the Hawaiian island of Molokai and also died of the disease.
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Leprosy, sometimes known as Hansen's disease, is an infectious disease caused by Mycobacterium leprae, an aerobic, acid fast, rod-shaped mycobacterium. The modern term for the disease is named after the discoverer of the bacterium, Gerhard Armauer Hansen. more...

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Sufferers of Hansen's disease have historically been known as lepers, however this term is falling into disuse as a result of the diminishing number of leprosy patients and the pejorative connotations of the term. In fact the term now that is most widely accepted among people and agencies working in the field of leprosy is 'people affected by leprosy'. The terms "leprosy" and "lepers" can also lead to public misunderstanding because the Bible uses these terms in reference to a wide range of skin conditions other than Hansen's disease.

Historically, leprosy was an incurable and disfiguring disease. Lepers were shunned and sequestered in leper colonies. Today, leprosy is easily curable by multidrug antibiotic therapy. The main challenges in the eradication of Hansen's disease is in reaching populations that have not yet received multidrug therapy services, improving detection of the disease, and providing patients with high-quality services and affordable drugs.

Other than humans, the only animals known to be susceptible to leprosy are the armadillo, mangabe monkeys, rabbits, and mice (on their footpads).


Hansen's disease has been recognized as a problem since the beginning of recorded history. It has been reported as early as 1350 BC in Egypt. "The oldest recorded disease" or "the oldest known disease" is a title given to this disease , as well as arthritis , gout , anthrax , schistosomiasis , and many other diseases. Lepers have frequently lived on the edge of society, and the disease was believed for a long time to have been caused by a divine (or demonic) curse or punishment. However, in the Middle Ages it was believed that lepers are cursed by humans, but loved by God.

During the Middle Ages, it was believed that leprosy was highly contagious and could be spread by the glance of a leper or an unseen leper standing upwind of healthy people. Nowadays, it is known that leprosy is only weakly contagious.

Minorities like the Navarrese agotes or French cagots were accused of being lepers.

Clinical features

The disease is caused by a mycobacterium which multiplies very slowly and mainly affects the skin, nerves, and mucous membranes. The organism has never been grown in bacteriologic media or cell culture, but has been grown in mouse foot pads and more recently in nine-banded armadillos. It is related to M. tuberculosis, the mycobacterium that causes tuberculosis. The difficulty in culturing the organism appears to be due to the fact that the organism is an obligate intra-cellular parasite that lacks many necessary genes for independent survival. The complex and unique cell wall that makes mycobacterium family difficult to destroy is apparently also the reason for the extremely slow replication rate.

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From Gale Encyclopedia of Medicine, 4/6/01 by Lata Cherath


Leprosy is a slowly progressing bacterial infection that affects the skin, peripheral nerves in the hands and feet, and mucous membranes of the nose, throat, and eyes. Destruction of the nerve endings causes the the affected areas to lose sensation. Occasionally, because of the loss of feeling, the fingers and toes become mutilated and fall off, causing the deformities that are typically associated with the disease.


Leprosy is also known as Hansen's disease after G. A. Hansen who in 1878 identified the bacillus Mycobacterium leprae that caused the disease.

The infection is characterized by abnormal changes of the skin. These changes, called lesions, are at first flat and red. Upon enlarging, they have irregular shapes and a characteristic appearance. The lesions are typically darker in color around the edges with discolored pale centers. Because the organism grows best at lower temperatures the leprosy bacillus has a preference for the skin, the mucous membranes and the nerves. Infection in and destruction of the nerves leads to sensory loss. The loss of sensation in the fingers and toes increases the risk of injury. Inadequate care causes infection of open wounds. Gangrene may also follow, causing body tissue to die and become deformed.

Because of the disabling deformities associated with it, leprosy has been considered one of the most dreaded diseases since biblical times, though much of what was called leprosy in the Old Testament most likely was not the same disease. Its victims were often shunned by the community, kept at arm's length, or sent to a leper colony. Many people still have misconceptions about the disease. Contrary to popular belief, it is not highly communicable and is extremely slow to develop. Household contacts of most cases and the medical personnel caring for Hansen's disease patients are not at particular risk. It is very curable, although the treatment is long-term, requiring multiple medications.

The World Health Organization (WHO) puts the number of identified leprosy cases in the world, at the beginning of 1997, at about 890,000. Seventy percent of all cases are found in just three countries: India, Indonesia, and Myanamar (Burma). The infection can be acquired, however, in the Western Hemisphere as well. Cases also occur in some areas of the Caribbean and even in southern Texas and Louisiana.

Causes & symptoms

The organism that causes leprosy is a rod-shaped bacterium called Mycobacterium leprae. This bacterium is related to Mycobacterium tuberculosis, the causative agent of tuberculosis. Because special staining techniques involving acids are required to view these bacteria under the microscope, they are referred to as acid-fast bacilli (AFB).

When Mycobacterium leprae invades the body, one of two reactions can take place. In tuberculoid leprosy (TT), the milder form of the disease, the body's immune cells attempt to seal off the infection from the rest of the body by surrounding the offending pathogen. Because this response by the immune system occurs in the deeper layers of the skin, the hair follicles, sweat glands, and nerves can be destroyed. As a result, the skin becomes dry and discolored and loses its sensitivity. Involvement of nerves on the face, arms, or legs can cause them to enlarge and become easily felt by the doctor. This finding is highly suggestive of TT. The scarcity of bacteria in this type of leprosy leads to it being referred to as paucibacillary (PB) leprosy. Seventy to eighty percent of all leprosy cases are of the tuberculoid type.

In lepromatous (LL) leprosy, which is the second and more contagious form of the disease, the body's immune system is unable to mount a strong response to the invading organism. Hence, the organism multiplies freely in the skin. This type of leprosy is also called the multibacillary (MB) leprosy, because of the presence of large numbers of bacteria. The characteristic feature of this disease is the appearance of large nodules or lesions all over the body and face. Occasionally, the mucous membranes of the eyes, nose, and throat may be involved. Facial involvement can produce a lion-like appearance (leonine facies). This type of leprosy can lead to blindness, drastic change in voice, or mutilation of the nose. Leprosy can strike anyone; however, children seem to be more susceptible than adults.

Well-defined skin lesions that are numb are the first symptoms of tuberculoid leprosy. Lepromatous leprosy is characterized by a chronic stuffy nose due to invasion of the mucous membranes, and the presence of nodules and lesions all over the body and face.

The incubation period varies anywhere from six months to ten years. On an average, it takes four years for the symptoms of tuberculoid leprosy to develop. Probably because of the slow growth of the bacillus, lepromatous leprosy develops even more slowly, taking an average of eight years for the initial lesions to appear.

It is not very clear how the leprosy bacillus is transmitted from person to person. Inhaling bacteria that are present in dust is thought to be one of the modes of transmission. However, even among people who live in the same household as the patient and are in close contact, only 5% get leprosy. It is obviously not a highly communicable disease. The incidence of leprosy is highest in the poverty belt of the globe. Therefore, environmental factors such as unhygienic living conditions, overpopulation, and malnutrition may also be contributing factors favoring the infection. The nine-banded armadillo is susceptible to this disease but it is still unclear if human infection is related to exposure to this animal.


One of the hallmarks of leprosy is the presence of AFB in smears taken from the skin lesions, nasal scrapings, or tissue secretions. In patients with LL leprosy, the bacilli are easily detected; however, in TT leprosy the bacteria are very few and almost impossible to find. In such cases, a diagnosis is made based on the clinical signs and symptoms, the type and distribution of skin lesions, and history of having lived in an endemic area.

The signs and symptoms characteristic of leprosy can be easily identified by a health worker after a short training period. There is no need for a laboratory investigation to confirm a leprosy diagnosis, except in very rare circumstances.

In an endemic area, if smears from an individual show the presence of AFB, or if he has typical skin lesions, he should definitely be regarded as having leprosy. Usually, there is slight discoloration of the skin and loss of skin sensitivity. Thickened nerves accompanied by weakness of muscles supplied by the affected nerve are very typical of the disease. One characteristic occurrence is a foot drop where the foot cannot be flexed upwards, affecting the ability to walk.


The most widely used drug for leprosy is dapsone. However, emergence of dapsone-resistant strains prompted the introduction of multi-drug therapy. The multi-drug therapy includes dapsone, refampin (also known as rifampicin), and clofazimine, all of which are powerful antibacterial drugs. Patients with MB leprosy are usually treated with all three drugs, while patients with PB leprosy are only given refampin and dapsone. Usually three months after starting treatment, a patient ceases being infectious, though not everyone with this disease is necessarily infectious before treatment. Depending on the type of leprosy, the time required for treatment may vary from six months to two years or more.

Each of the drugs have minor side effects. Dapsone can cause nausea, dizziness, palpitations, jaundice and rash. A doctor should be contacted immediately if a rash develops. Dapsone also interacts with the second drug, refampin. Refampin increases the metabolizing of dapsone in the body, requiring an adjustment of the dapsone dosage. Refampin may also cause muscle cramps, or nausea. If jaundice, flu-like symptoms or a rash appear, a doctor should be contacted immediately. The third drug, clofazimine may cause severe abdominal pain and diarrhea, as well as discoloration of the skin. Red to brownish black discoloration of the skin and bodily fluids, including sweat, may persist for months to years after use.

Thalidomide, the most famous agent of birth defects in the 20th century, is now being used to treat complications of leprosy and similar diseases. Thalidomide regulates the immune response by suppressing a protein, tumor necrossi factor alpha.

Leprosy patients should be aware that treatment itself can cause a potentially serious immune system response called a lepra reaction. When antibiotics kill M. leprae, antigens (the proteins on the surface of the organism that initiate the body's immune system response) are released from the dying bacteria. In some people, when the antigens combine with the antibodies to M. Leprae in the bloodstream, a reaction called erythema nodosum leprosum may occur, resulting in new lesions and peripheral nerve damage. Cortisone-type medications and, increasingly, thalidomide are used to minimize the effects of lepra reactions.


Leprosy is curable; however, the deformities and nerve damage associated with leprosy are often irreversible. Preventions or rehabilition of these defects is an integral part of management of the disease. Reconstructive surgery, aimed at preventing and correcting deformities, offers the greatest hope for disabled patients. Sometimes, the deformities are such that the patients will not benefit from this type of surgery.

Comprehensive care involves teaching patients to care for themselves. If the patients have significant nerve damage or are at high risk of developing deformities, they must be taught to take care of their insensitive limbs, similar to diabetics with lower leg nerve damage. Lacking the sensation of pain, the patients should constantly check themselves to identify cuts and bruises. If adequate care is not taken, these wounds become festering sores and a source of dangerous infection. Physiotherapy exercises are taught to the patients to maintain a range of movement in finger joints and prevent the deformities from worsening. Prefabricated standardized splints are available and are extremely effective in correcting and preventing certain common deformities in leprosy. Special kinds of footwear have been designed for patients with insensitive feet in order to prevent or minimize the progression of foot ulcers.


By early diagnosis and appropriate treatment of infected individuals, even a disease as ancient as leprosy can be controlled. People who are in immediate contact with the leprosy patient should be tested for leprosy. Annual examinations should also be conducted on these people for a period of five years following their last contact with an infectious patient. Some physicians have advocated dapsone treatment for people in close household contact with leprosy patients.

The WHO Action Program for the Elimination of Leprosy has adopted a resolution calling for the reduction of leprosy's prevalence to less than one case per 10,000 people by the year 2000. In order to make this possible, educating people about the disease and raising their awareness is of utmost importance. The tuberculosis BCG vaccine, used in many areas of the world, may have an effect in decreasing the incidence of leprosy.

Key Terms

Endemic area
A geographical area where a particular disease is prevalent.
Death of tissue due to loss of blood supply followed by bacterial invasion and putrefaction.
Incubation period
The time it takes for symptoms to develop after initial exposure to a disease-causing organism.
Any visible, local abnormality of the tissues of the skin, such as a wound, sore, rash, or boil.
Mucous membranes
The inner tissue that covers or lines body cavities or canals open to the outside, such as nose and mouth. These membranes secrete mucus and absorb water and salts.
Nasal scraping
Pathological material obtained for clinical study by scratching the inner surface of the nose with a clinical instrument.
A small mass of tissue in the form of a protuberance or a knot that is solid and can be detected by touch.
Any disease-producing agent or microorganism.
A specimen prepared for microscopic study by spreading the material across a slide and treating it with a specific stain.

Further Reading

For Your Information


  • "Bacterial and Mycotic Infections: Leprosy." In Microbiology, 3rd ed., edited by B. D. Davis, et al. New York: Harper & Row Publishers, 1980.
  • Krane, Stephen M., and Michael F. Holick. "Mycobacterial Diseases: Leprosy." In Harrison's Principles of Internal Medicine, edited by R.G. Petersdorf, et al. New York: McGraw-Hill, 1994.
  • Zinsser, Hans. Zinsser Microbiology, 19th ed., edited by Wolfgang K. Joklik, et al. Norfolk, CT: Appleton and Lange, 1988.


  • Binford, Chapman et al. "Leprosy." Journal of the American Medical Association 247 (April 23-30, 1982): 2283-2292.


  • American Leprosy Missions. 1 ALM Way, Greenville, SC 29601. (1-800-LEPROSY).
  • British Leprosy Relief Association, LEPRA. Fairfax House, Causton Road, Colchester, Essex CO1 1PU, UK.
  • INFOLEP, Leprosy Information Services. Postbus 95005,1090 HA, Amsterdam, Netherlands. Infolep@antenna.nl.
  • WHO/LEP, Action Programme for the Elimination of Leprosy. 20 Avenue Appia CH-1211, Geneva 27, Suisse. (http://www.who.ch/programmes/lep/lep_home.htm).


  • National Institutes of Health. Leprosy. http://www.search.info.nih.gov.
  • U.S. government. Leprosy. http://www.healthfinder.nih.gov.

Gale Encyclopedia of Medicine. Gale Research, 1999.

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