Gangrenous hand. Fingers and wrist of a patient suffering from a dry form of gangrene, also known as mummification necrosis. This occurs when blood supply to a digit or limb gradually slows and then ceases, thereby depriving tissues of oxygen, which causes cell and tissue death. The fingers have turned black, and have become dry and shrivelled. There is no infection with dry gangrene and it is usually not painful or dangerous. The affected part will probably fall off eventually without the need for surgical intervention. Reduced blood flow might be caused by injury, atherosclerosis (hardening of the arteries), poor circulation or diabetes.