Classification of Leprosy.

             Leprosy is classified according to symptoms and histopathology (abnormalities of tissue cells affected by the disease). Patients with leprosy are classified into two general groups: those diagnosed as having paucibacillary leprosy possess five or fewer skin lesions and those diagnosed with multibacillary leprosy have six or more skin lesions. The disease can be further classified on the basis of skin findings, motor and sensory changes, and biopsy findings as indeterminate (I), tuberculoid (T), borderline tuberculoid (BT), borderline (BB), borderline lepromatous (BL), and lepramtous (LL). Under the WHO classification, I, TT, and BT diseases are generally equivalent to paucibacillary leprosy while, BB, BL, and LL are equivalent to multibacillary disease (Jacobson & Krahenbuhl, 1999). Leprosy is classified according to a continuum with indeterminate being the earliest stage of the disease and lepramtous as the most advanced stage. Usually the disease is first diagnosed when a few or single macules (a patch of skin that is altered in color but usually not elevated) are found on the body. As the disease progress, the macules tend to become elevated from the skin (called papules and nodules) and become larger in number. As these nodules begin to spread, motor and sensory impairments begin to occur. Finally the last stage of the disease (the lepramotous phase) results in multiple nodules or lesions, loss of hair and secondary sexual characteristics, severe nerve damage with complete loss of sensation in the areas around the lesions, destruction and absorption of bone occur at this point which results in the loss of extremities, as well as a flattening of the bridge of the nose which produces the "leonine faces" associated with the disease. .

             Mechanism of Infection.

             As mentioned previously, leprosy infects the skin, mucous membrane, and peripheral nerves.