Leprosy is an infectious disease caused by the bacterium Mycobacterium leprae. This disease causes skin sores, nerve damage, and muscle weakness that gets worse over time.
Leprosy is not very contagious and has a long incubation period (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 on by coming into 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, and in temperate, tropical, and subtropical climates. About 100 cases per year are diagnosed in the United States. Most cases are in the South, California, Hawaii, and US islands, and Guam.
Drug-resistant Mycobacterium leprae and an increased numbers of cases worldwide have led to global concern for this disease.
Several antibiotics are used to kill the bacteria that cause the disease. These include dapsone, rifampin, clofazamine, fluoroquinolones, macrolides, and minocycline. 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 limits damage, prevents a person from spreading the disease, and reduces 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 due to repeated injury because they lack feeling in those areas.
When to Contact a Medical Professional
Call 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.
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.
Review Date 8/25/2019
Updated by: Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant 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.