Treponema pallidum causes syphilis, the sexually transmitted disease historically linked to the 1905 discovery of its pathogen.
This bacterium is a spirochete, a slender organism with a spiral shape and internal structures that help it move through tissue. Syphilis can progress through several stages, beginning with a usually painless sore and potentially causing widespread symptoms or serious nervous-system and cardiovascular disease when untreated.
German zoologist Fritz Schaudinn and dermatologist Erich Hoffmann reported the organism in 1905. The subspecies pallidum causes venereal syphilis; related subspecies cause other treponemal diseases such as yaws. Borrelia burgdorferi is also a spirochete, but it causes Lyme disease rather than syphilis.