Contributor: Gordon K. Klintworth
Leprosy (Hansen disease, elephantiasis grecorum, Lucio disease, Hanseniasis) is an Mycobacterium infection caused by Mycobacterium leprae. 10-12 million people are infected worldwide. The disease is most prevalent in the tropics and subtopics (Africa, Mexico, Central America, Middle East, India, Southern Europe, China, Southeast Asia). It also still occurs in the Southern United States. The skin and peripheral nerves are affected most often, but the respiratory system, vascular endothelium and reticuloendothelial system may be involved. Lesions of the cornea may be prominent. The reaction to Mycobacterium leprae varies with the cell-mediated immunity of the host and ranges from lepromatous leprosy [leprosy - lepromatous] to tuberculoid leprosy [leprosy - tuberculoid]. Hansen disease needs to be differentiated from other conditions associated with a xanthogranulomatous reaction (xanthogranuloma), sarcoidosis, berylliosis, silica-induced granulomas [granuloma - silica induced], other causes of Mycobacterium infection, fungal infection and granuloma annulare.