Leprosy is an ancient disease caused by a bacillus which is very similar to the tuberculosis bacillus. The main difference is that the leprosy bacillus attacks the skin and the nerves of the limbs and face. Because the nerves are sometimes destroyed, patients lose sensation in their hands and feet and can therefore unwittingly burn or injure themselves. Destruction of the nerves also causes paralysis of muscles in the hands and feet, and, if good care and treatment are not available, this leads to the deformity classically associated with leprosy. It may be several years after the infection is contracted that signs and symptoms of the disease appear.