Syphilis is a sexually transmitted disease caused by the bacterium Treponema pallidum. Primary syphilis presents as a small painless open sore 3 to 6 weeks after exposure. Although the lesion heals within 6 to 8 weeks, the untreated organism will continue to multiply unchecked, causing many complications. Infection may last for 30 years or more and result in severe neurological complications.
Review Date 10/25/2020
Updated by: Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.