Leprosy is a disease caused by the bacterium Mycobacterium leprae. This disease causes skin sores, nerve damage, and muscle weakness that gets worse over time.
Leprosy does not spread easily. It also takes a long time before symptoms appear, which makes it hard to know where or when someone caught the disease. Children are more likely than adults to get the disease.
Most people who come in contact with the bacteria don't develop the disease. This is because their immune system is able to fight off the bacteria. Experts believe that the bacteria spread when a person breathes in tiny airborne droplets released when someone with leprosy coughs or sneezes. The bacteria may also be passed through contact with the nasal fluids of a person with leprosy. Leprosy has two common forms: tuberculoid and lepromatous. Both forms produce sores on the skin. However, the lepromatous form is more severe. It causes large lumps and bumps (nodules).
Leprosy is common in many countries worldwide including India, Brazil and Indonesia. It is also found in temperate, tropical, and subtropical climates. About 150 to 250 cases per year are diagnosed in the United States. Most new cases in the United States were in:
- New York
Drug-resistant Mycobacterium leprae and an increased numbers of cases worldwide have led to global concern for this disease.
- Skin lesions that are lighter than your normal skin color
- Lesions that have decreased sensation to touch, heat, or pain
- Lesions that do not heal after several weeks to months
- Muscle weakness
- Numbness or lack of feeling in the hands, arms, feet, and legs
Exams and Tests
Tests that are done include:
- Skin lesion biopsy
- Skin scraping examination
The lepromin skin test can be used to tell the two different forms of leprosy apart. This test is not used to diagnose the disease.
Several antibiotics are used to kill the bacteria that cause the disease. These include:
More than one antibiotic is often given together, and usually for months.
Aspirin, prednisone, or thalidomide is used to control inflammation.
Diagnosing the disease early is important. Early treatment helps:
- Limit the damage
- Prevent a person from spreading the disease
- Reduce long-term complications
Health problems that may result from leprosy include:
- Muscle weakness
- Permanent nerve damage in the arms and legs
- Loss of sensation
People with long-term leprosy may lose the use of their hands or feet. This is due to repeated injury because they lack feeling in those areas.
When to Contact a Medical Professional
Contact your health care provider if you have symptoms of leprosy, especially if you have had contact with someone who has the disease. Cases of leprosy in the United States are reported to the Centers for Disease Control and Prevention.
People on long-term medicine become noninfectious. This means they do not transmit the organism that causes the disease.
Centers for Disease Control and Prevention website. Hansen's disease (leprosy).
Centers for Disease Control and Prevention website. World Leprosy Day: bust the myths, learn the facts.
Dupnik K. Leprosy (Mycobacterium leprae). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 250.
Ernst JD. Leprosy (Hansen disease). In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 310.
Last reviewed on: 9/1/2021
Reviewed by: Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. Editorial update May 25, 2022.