Here’s a rundown of the stages of syphilis, with the usual symptoms and potential for complications of each stage.

Primary stage: Early in the infection, a painless sore, called a chancre, crops up wherever the bacteria first entered your body. A chancre may be visible or hidden inside your mouth, vagina, cervix, anus, or elsewhere. These initial chancres usually heal within a month or two.

Secondary stage: Widespread rashes often occur in secondary syphilis and last about two to six weeks. This stage can also involve symptoms that mimic other common conditions, including the flu, psoriasis, and hemorrhoids. Secondary-stage symptoms go away on their own, yet the infection lingers.

Extreme complications during the primary and secondary stages are rare but do sometimes occur. For instance, while severe damage to the heart and blood vessels usually occurs in the last stage of syphilis, such damage can also occur early in the illness. Doctors have seen people with early-stage syphilis who needed valve replacement and coronary bypass operations.

Latent stage: This symptom-free stage may last for a few years or for the rest of your life. In those who receive no treatment, about one-third of such cases progress to late, or tertiary, syphilis, during which many severe complications can occur.

Late, or tertiary, syphilis: The late stage of syphilis is when the most severe complications usually arise. Here’s a partial list:

Gummas Small bumps or tumors called gummas can arise on your skin, bones, liver, or any other organ, including the stomach and eyes. Gummas often arise in the palate and the structures of the nose. Other common sites include the face, scalp, trunk, and legs.
Neurological problems Syphilis can cause many nervous system problems, including sudden, searing pains. These spasms of pain may occur in various organs, often the stomach, and they may cause vomiting. Extreme, lightning-like pains in your rectum, bladder, and larynx may also occur. Syphilis can also cause the loss of sensation and of responsiveness to temperature changes. Visual problems or blindness, meningitis (inflammation of the brain), and stroke may occur. Nervous system damage can also cause incontinence and impotence in men.
Cardiovascular problems These usually arise between 10 and 25 years after the initial syphilis infection. They may include inflammation and bulging of the aorta, the body’s main artery. Syphilis may also attack other blood vessels and heart valves.
Pituitary gland involvement Rarely, syphilis can cause hypopituitarism, in which the pituitary gland secretes reduced amounts of hormones. In adults, this can cause premature aging, among other issues, and in children, dwarfism.
Heightened risk for HIV infection Sores caused by syphilis provides an easy path into the body for HIV. As a result, both men and women with syphilis have a risk of contracting HIV that is about two to five times higher than in adults who don’t have syphilis.
Gastric syphilis This relatively rare complication, affecting the stomach, usually strikes people in their twenties to forties. It can cause pain, loss of appetite, nausea, vomiting, and weight loss.
Pregnancy and childbirth complications If you have syphilis while pregnant, you can pass it on to your child. Infected infants are at risk of being born with or developing many deformities. Syphilis during pregnancy greatly raises the risk of miscarriage or stillbirth, and infants who acquire syphilis from their mothers are at serious risk for dying during or shortly after birth.