Most cases of leprosy can be diagnosed and classified without histopathological examination. However, examination of a biopsy specimen for histopathology can be a valuable aid to differential diagnosis and for detailed classification of the disease. It plays an important role in research as well.

Leprosy is one disease, yet it may like many diseases. It is caused by Mycobacterium leprae & manifests differently in different persons according to the immunological response of their bodies to the M. leprae. Ridley and Jopling proposed a classification system based on the different resistance of patients to M. leprae, shown in the picture here.