Mycobacterium leprae is a bacteria. It causes the disease, leprosy, also known as Hanson's Disease. The bacterium was discovered in 1873 by a Norwegian doctor named Gerhard Armauer Hansen. "M. leprae" is a gram-positive, aerobic rod surrounded by the characteristic waxy coating unique to Mycobacteria. In size and shape, it closes resembles M. tuberculosis. Due to its thick, waxy coating, stains with carbol-fuchsin are used, rather than with the traditional Gram staining method.