October 5, 2011

Treponema pallidum

Syphilis is a sexually transmitted disease caused by the bacterium Treponema pallidum. Syphilis is a potentially progressive disease that if untreated may cause debilitating disease of the entire body. Syphilis currently is of particular concern because it is believed to increase the transmission of HIV.

Syphilis is transmitted during sexual or nonsexual contact with a person who is infected. The bacterium initially spreads from the infected person to the skin or genital area of the uninfected person. Syphilis can also be transmitted in utero. Syphilis cannot be spread by toilet seats, doorknobs, swimming pools, hot tubs, shared clothing, or eating utensils.

The symptoms of syphilis vary according to the stage of disease. The stages of syphilis are divided into primary, secondary, latent, and tertiary disease. The initial lesion of primary syphilis is a genital ulcer called a “chancre.” It may appear between 10 and 90 days after a person comes in contact with the bacteria. Newly infected people are often unaware of the ulcer, since it is painless and usually disappears within 3-6 weeks with or without treatment. Secondary syphilis is usually characterized by a skin rash. The rash can appear anywhere on the body, but is almost always on the palms of the hands and soles of the feet. It does not itch, and may be very faint and not noticeable. The rash usually disappears within several weeks. Other symptoms during this stage may include fever, fatigue, headache, and swollen lymph glands. If syphilis remains untreated, the disease may go into the latent stage. People at this point usually have no further signs or symptoms of disease. Tertiary syphilis is characterized by systemic disease, but not all patients who develop secondary syphilis will develop tertiary syphilis. At this point, the bacteria can damage almost any part of the body, particularly the nervous system, bones, and joints. This stage can last for years or even decades. Untreated syphilis can be responsible for blindness and neurological problems, mental illness, heart disease, and potentially death.

Clinical symptoms of syphilis, especially the early symptoms, can be confusing, mimicking other diseases. The diagnosis of syphilis is made by a blood test. Because the blood test can have “false positives,” another blood test is always used to confirm the diagnosis. Identifying the syphilis bacteria under the microscope is another way of diagnosing the disease, but requires specialized equipment not available to most physicians.

Syphilis usually responds well to injectable penicillin. There are other antibiotics available for patients who have penicillin allergies. Unfortunately, during the first stages of syphilis, many people do not realize that they are infected, and usually do not seek treatment. Once a person is treated, the blood test can be followed to make sure that the infection is gone. People with more advanced stages of syphilis usually require longer courses of treatment. Patients who present with syphilis should always be tested for HIV. Ulcers due to syphilis increase the risk of acquisition of HIV, and advanced HIV infection alters the clinical presentation of syphilis and makes central nervous system complications more likely.

Women who have syphilis early in their pregnancy have a higher rate of miscarriage. Pregnant women who do not miscarry have a 40-70% chance of passing syphilis on to their unborn child, depending on the stage of their disease. Congenital syphilis can cause serious fetal and neonatal complications, including stillbirth, neonatal jaundice (yellow skin), swollen limbs and spleens, and skin ulcers and rashes. All women should be tested at their first prenatal visit for syphilis, and women who are at higher risk for acquiring syphilis should be tested again later in their pregnancy.

Syphilis, like many sexually transmitted diseases, can be prevented by practicing safe sex and using latex condoms properly and consistently. While initial syphilis infection may not always be preventable, getting screened if you are at high risk, and being treated early, reduces the likelihood that complications of late-stage disease will develop.

See Also: Acquired immunodeficiency syndrome, Chlamydia, Gonorrhea, Herpes simplex virus, Human papillomavirus, Sexually transmitted diseases

Suggested Reading

  • Gripshover, B., & Valdez, H. (2002). Common sexually transmitted diseases. In J. S. Tan (Ed.), Experts guide to the management of common infectious diseases (pp. 271-303). Philadelphia: American College of Physicians.

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