This is chronic infection due to Treponema pallidum. It is convenient to describe untreated syphilis in three stages – primary, secondary and tertiary. It must be realized, however, that the disease is generalized and continuous from the time of infection, and that it may be almost completely latent during its long course which may last for over 30 years.
Primary Stage. The primary lesion (chancre) develops at the site of infection. It occurs usually on the genitals, but it may be found on the lips, in the mouth, at the anus, or on a finger. The incubation period is 10 days to 10 weeks. A small painless indurated swelling forms and usually ulcerates. The regional lymph nodes are enlarged, firm, painless and seldom suppurate.