Complications of Mycobacterium leprae
The above condition is probably what you think of when you hear ‘leprosy’; disfigurement and limbs falling off. These are not actually symptoms caused directly by M. leprae, but are complications of long exposure to it. Prior to the effective forms of modern medicine some of us enjoy today, once an individual was infected with M. leprae, life long exposure and disfigurement was a guarantee. Today, leprosy is very treatable.
The reason digits and extremities decay in extreme cases is because of the damage M. leprae reaps on the peripheral nerves (which your hands have a high density of). Without feeling in your extremities, you become prone to damaging them without realizing, cutting off their blood flow, wrist/foot-drop, absorption of digits, clawing of toes and hands, and possibly contracture.