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Definition: A sexually transmitted disease caused by the spirochete Treponema pallidum that is characterized in its primary stage by genital sores. If untreated, skin ulcers develop in the next stage, called secondary syphilis. As the disease progresses to potentially fatal tertiary syphilis, neurologic involvement with weakness and skeletal or cardiovascular damage can occur.
Source: The American Heritage Science Dictionary. Boston: Houghton Mifflin, 2005. Credo Reference. Web. 17 August 2012.