Leprosy is caused by Mycobacterium leprae, an  acid –fast, rod-shaped bacillus.  This  affects mainly in the skin. It may occur in all ages from infant to the old  age.  The chronic course of leprosy is  incurable and physical abilities are never been calculated.  G.A. Hansen discovered mycobacterium leprae  in the early 1873 causing diseases in human being. But the leprosy was only  founded from 1940s. The cardinal signs of this disease are skin lesion  consistent with definite sensory loss, with or without thickened nerves.  Leprosy can be classified in to two types like the persons showing negative  smears are grouped as paucibacillary leprosy, while the positive smears are  grouped as multibacillary leprosy.  The  person with multibacillary leprosy is not treated with regimen for the  paucibacillary leprosy.  The typical  feature of leprosy is sensory loss.  It  is due to the damage in the nerves, the loss of sensation in the skin happens.  The muscle also weakens which is supplied by the affected nerve.