A chronic disease that causes lesions on the bones, skin, mucous membranes, and peripheral nervous system. People suffering from leprosy often lose sensation in their limbs and extremities because of nervous system lesions, and can unknowingly injure themselves and/or not care for wounds, thus causing further disfigurement. This disease, which was widely feared in ancient times and is still a problem in undeveloped countries, is caused by the Gram-positive, rod-shaped bacterium Mycobacterium leprae. Armadillos can also catch this disease (there have been a few isolated incidents of people catching leprosy from them) and so are used in medical research on the illness.