infectious diseases
Leprosy
Pathophysiology of Leprosy
Humans are the main natural reservoir forM. leprae. Armadillos are the only confirmed source other than humans, although other animal and environmental sources may exist. Leprosy is thought to be spread by passage from person to person through nasal droplets and secretions. Casual contact (eg, simply touching someone with the infection) and short-term contact does not seem to spread it. About half of people with leprosy probably contracted it through close, long-term contact with an infected person. Even after contact with the bacteria, most people do not develop leprosy; health care workers often work for many years with people who have leprosy without contracting it. Most immunocompetent people who are infected withM. lepraedo not develop leprosy because of effective immunity. People who do develop leprosy probably have a poorly defined genetic predisposition. M. lepraegrow slowly (doubling in 2 weeks). The usual incubation period ranges from 6 months to 10 years. Once infection develops, hematogenous dissemination can occur. Leprosy is classified by type and number of skin areas affected: Paucibacillary:≤5 skin lesions with no bacteria detected on samples from those areas Multibacillary:≥6 skin lesions, bacteria detected on samples from skin lesions, or both Leprosy also is classified by cellular response and clinical findings: Tuberculoid Lepromatous Borderline People with tuberculoid leprosy typically have a strong cell-mediated response, which limits disease to a few skin lesions (paucibacillary), and the disease is milder, less common, and less contagious. People with lepromatous or borderline leprosy typically have poor cell-mediated immunity toM. lepraeand have more severe, systemic infection with widespread bacterial infiltration of skin, nerves, and other organs (eg, nose, testes, kidneys). They have more skin lesions (multibacillary), and the disease is more contagious. In both classifications, the type of leprosy dictates Long-term prognosis Likely complications Duration of antibiotic treatment 