Explore the recorded discovery and history of Mycobacterium leprae, with source links and stated limits.
WHO describes leprosy as a chronic infectious disease caused by Mycobacterium leprae that affects skin and peripheral nerves and can cause permanent disabilities if untreated. StatPearls describes M. leprae as a Gram-positive, acid-fast bacillus and an obligate intracellular organism that cannot be cultured with artificial media, with a predisposition to spread more efficiently at cooler regions of the body including skin, superficial nerves and the membranes of the upper respiratory tract, and tropism for Schwann cells and macrophages. LPSN records that no culture is available for this species. WHO states that leprosy is a curable disease and recommends multidrug therapy for 6 months in paucibacillary cases or 12 months in multibacillary cases, and that patients become non-infectious once treatment begins.
LPSN records the basonym “Bacillus leprae” Hansen 1880. Gerhard Armauer Hansen’s identification of a bacterium in leprosy lesions is why the disease is also called Hansen’s disease — a name chosen partly to move away from the stigma attached to the older word.
LPSN records Mycobacterium leprae (Hansen 1880) Lehmann and Neumann 1896, effectively published in their Atlas und Grundriss der Bakteriologie and retained on the 1980 Approved Lists of Bacterial Names. LPSN notes there is no culture available, so the species has no type strain in culture collections.
These references do not identify a first person ever infected. Leprosy is described in historical and archaeological records long before 1880, so the identification of the organism dates a scientific milestone rather than a first case or a geographic origin.
Source check: 2026-09-20. Educational content; independent scientific review remains pending.