Leprosy. Open wound due to leprosy (Hansen's disease) on an elderly man's leg. The patient is now free from infection. Leprosy is a chronic disease caused by the bacterium Mycobacterium leprae. It affects the skin and mucous membranes, and irreversibly damages nerves. In serious cases, swelling of the nerves, numbness of the skin, muscle weakness and paralysis follow. The loss of feeling means that injuries may not be noticed, leading to scarring or even the loss of fingers and toes. The disease is treated with antibacterial drugs. Photographed in Samoa in 1999.