Leprosy. Coloured transmission electron micrograph (TEM) of a section through a nerve axon (yellow) enclosed by a myelin sheath (dark brown) that is degenerating due to leprosy (Hansen’s disease). The fatty myelin sheath is normally unbroken, insulating the axon which carries nerve signals to allow the rapid passage of nerve impulses. While leprosy is caused by the bacterium Mycobacterium leprae, most of the symptoms result from the immune system’s response to this micro- organism. The damage to nerve tissue can result in a loss of sensation, muscle paralysis, deformity and blindness. Magnification: x4375 at 5x7cm size. Magnification:x15,000 at 6.5×9.5 inch size.