Syphilis is caused by the spirochete Treponema pallidum. Clinical syphilis usually is subdivided into primary, secondary, latent, and tertiary (late) stages. The primary stage begins after an average incubation period of 3-6 weeks (range, 1.5-13 weeks) and is manifested by the development of a primary stage shallow ulcer, or chancre, near the site of infection. The time of appearance is variable, and the lesion often is inconspicuous and overlooked, especially in the female. The primary stage lasts about 4-6 weeks (range, 2-8 weeks) during which the chancre usually heals, followed by the secondary stage, which lasts about 4-12 weeks. About 80% of patients develop a rash, which in addition to other areas typically involves the palms and soles. Mucous membranes are involved in about 60% of cases. There is generalized lymphadenopathy in 75%. Asymptomatic central nervous system (CNS) involvement has been documented in up to 30% of patients. During the last part of the secondary stage the visible lesions disappear and the patient enters the latent stage. This lasts, on the average, 3-5 years. About 25% of patients relapse temporarily into active disease during the first 1-2 years. By the end of the latent period about one half of untreated patients apparently achieve spontaneous cure or at least do not develop further evidence of the infection. About 25% remain in a latent (“late latent”) status, and the remaining 25% develop tertiary stage sequelae such as neurologic, cardiovascular, or ocular syphilis.

Diagnostic procedures in syphilis include dark-field examination, immunologic tests, and cerebrospinal fluid (CSF) examination, depending on the clinical situation.