Primary syphilis, the first stage, causes one or more firm, round sores at the infection site that may be painless, states the Centers for Disease Control and Prevention. The secondary stage typically causes mouth and genital sores or skin rashes that are red or reddish brown with a rough texture.
The secondary stage usually starts when the primary sore has healed, and the rashes commonly appear on the soles of the feet and palms of the hands, according to the CDC. During this stage, men may also notice swollen lymph glands, fatigue, muscle aches, weight loss and patchy hair loss. Other symptoms include fever, headaches and sore throat. The symptoms gradually disappear, but the infection continues to progress, increasing the risk of developing the most severe stage.
Latent syphilis is a dormant period that follows the secondary stage and causes no symptoms, Mayo Clinic explains. In an untreated man, the latent stage can last indefinitely. If the infection progresses to the tertiary stage, it can cause damage to the brain, nerves, bones and joints or interfere with heart, eye, liver and blood vessel functions. Between 15 and 30 percent of untreated people develop tertiary syphilis, which may manifest years after the initial infection. Men with male partners have the highest risk of contracting syphilis, but an-early stage infection is easily treatable with one dose of penicillin. Doctors administer multiple doses for men with late-stage syphilis.