Leprosy, also known as Hansen’s disease (HD), is a long-term infection by the bacteria Mycobacterium leprae or Mycobacterium lepromatosis. Infection can cause severe damage to the nerves, skin, eyes, and lining of the nose (nasal mucosa). Leprosy is contagious and spreads through close contact with an infected person. It most commonly affects adults in warm climates. Early diagnosis and treatment is essential to prevent disability.
There are two main types of leprosy: paucibacillary (PB) and multibacillary (MB). PB leprosy has one to five skin lesions or nodules and few if any bacteria in the body. MB leprosy has more than five skin lesions or nodules and many bacteria in the body. People with MB disease are more likely to infect others than those with PB disease.
The first signs of leprosy are usually pale patches on the skin that have decreased sensation to touch, temperature, or pain. These spots are called hypopigmented macules. Nodules may also develop on the skin; these raised bumps are filled with bacteria and pus and often occur on areas exposed to light pressure, like elbows, knees, hands, and feet. The loss of sensation in affected areas can lead to repeated injury and ulceration of tissues; these wounds may become secondarily infected leading to further tissue destruction. In some cases deformities can occur due to nerve damage; for example fingers may become shortened and claw-like from repeated injuries (called ulnar drift).
Leprosy is diagnosed by examining a person’s skin lesions under a microscope or through biopsy (taking a small sample of tissue from a lesion). Treatment involves taking specific antibiotics for several months that kill the bacteria causing leprosy; however, they do not repair any nerve damage that may have already occurred. After successful treatment people with PB disease are no longer infectious while people with MB disease remain infectious for some time after starting treatment but eventually become noninfectious as well. There is no vaccine available for prevention of leprosy at this time