Alternative names 
Hansen’s disease

Leprosy is an infectious disease that has been known since biblical times. It is characterized by disfiguring skin lesions, peripheral nerve damage, and progressive debilitation.

Causes, incidence, and risk factors

Leprosy is caused by the organism Mycobacteriumleprae. It is a difficult disease to transmit and has a long incubation period, which makes it difficult to determine where or when the disease was contracted. Children are more susceptible than adults to contracting the disease.

Leprosy has two common forms, tuberculoid and lepromatous, and these have been further subdivided. Both forms produce lesions on the skin, but the lepromatous form is most severe, producing large disfiguring nodules.

All forms of the disease eventually cause peripheral neurological damage (nerve damage in the extremities) manifested by sensory loss in the skin and muscle weakness. People with long-term leprosy may lose the use of their hands or feet due to repeated injury resulting from lack of sensation.

Leprosy is common in many countries in the world, and in temperate, tropical, and subtropical climates. Approximately 100 cases per year are diagnosed in the U.S. Most cases are limited to the South, California, Hawaii, and U.S. island possessions.

Effective medications exist, and isolation of victims in “leper colonies” is unnecessary. The emergence of drug-resistant Mycobacterium leprae, as well as increased numbers of cases worldwide, have led to global concern about this disease.


Symptoms include:

  • one or more hypopigmented (lighter than your normal skin color) skin lesions that have decreased sensation to touch, heat, or pain  
  • skin lesions that do not heal after several weeks to months  
  • numbness or absent sensation in the hands and arms, or feet and legs  
  • muscle weakness resulting in signs such as foot drop (the toe drags when the foot is lifted to take a step)

Signs and tests

  • Lepromin skin test can be used to distinguish lepromatous from tuberculoid leprosy, but is not used for diagnosis.  
  • Skin scraping examination for acid fast bacteria

Medications used to eliminate the microorganism and to reduce symptoms include:

  • Dapsone  
  • Rifampin  
  • Clofazimine  
  • Ethionamide  
  • Aspirin, prednisone, or thalidomide are used for the control of inflammation (e.g., “erythema nodosum leprosum”) that may occur with therapy

Expectations (prognosis)
Early recognition is important. Early treatment limits damage by the disease, renders the person noninfectious, and allows for a normal lifestyle.


  • permanent nerve damage  
  • cosmetic disfigurement

Calling your health care provider
Call your health care provider if signs or symptoms described here occur, especially following exposure. Cases of leprosy in the United States need to be reported to the Centers for Disease Control and Prevention.

Prevention consists of avoiding close physical contact with untreated people. People on long-term medication become noninfectious (they do not transmit the organism that causes the disease).

Johns Hopkins patient information

Last revised: December 7, 2012
by Sharon M. Smith, M.D.

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