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Syphilis, also called lues, is a sexually transmitted disease caused by a type of bacteria (treponema pallidum), marked by three clear stages over a period of years. Any organ system may become involved. The first stage (primary syphilis) is marked by the appearance of a small, painless, red pus-forming bump on the skin or mucous membrane between 10 and 90 days after exposure. The second stage (secondary syphilis) occurs about 2 months later, after the bacteria have increased in number and spre