Leprosy is a disease which affects the skin and mucous membranes which causes the skin's surface to form lumps and discolouration. It is caused by an intracellular infection by the bacteria Mycobacterium leprae. The body responds in two different ways to this infection which causes different outcomes:
- Tuberculoid leprosy - the body produces a strong TH1 response which kills a lot of the bacteria and the disease progresses slowly.
- Lepromatous leprosy - the body produces a strong TH2 antibody response which leaves a lot of macrophages infected with the bacteria as antibodies are not a good response to an intracellular infection. As a result this form of leprosy is fatal.