Syphilis

Illustration of a syphilis bacterium.

Syphilis is a sexually transmitted disease (STD) caused by an infection with bacteria known as Treponema pallidum. 

Like other STDs, syphilis can be spread by any type of sexual contact. Syphilis can also be spread from an infected mother to the fetus during pregnancy or to the baby at the time of birth.

Syphilis has been described for centuries. It can cause long-term damage to different organs if not properly treated.

Syphilis infection, when untreated, progresses through different clinical stages with characteristic signs and symptoms. 

Primary syphilis

The first, or primary, stage of syphilis is characterized by the formation of a painless ulcer known as a chancre. This sore develops at the site of infection and is usually solitary. A chancre is usually firm and round in shape. Sometimes, multiple chancres may be present. The chancre contains infectious bacteria and while the sore is present, the condition is highly contagious. 

Symptoms typically develop at around 21 days after the infection, but they may appear anywhere from 10 to 90 days following infection.

Transmission: Any contact with the chancre can spread the infection. If the chancre is located in the mouth, for example, even kissing can spread the disease. The chancre lasts for about 3 to 6 weeks and typically then goes away on its own. The use of condoms may also not prevent the spread of the illness if the chancre is located on an area of the body not covered by the condom.

Secondary syphilis

If primary syphilis is left untreated, secondary syphilis may develop. This stage of the illness usually occurs a few weeks to several months after the primary stage. 

Secondary syphilis is characterized by a skin rash that typically does not itch and may easily be mistaken for rashes caused by other illnesses. It may appear on almost any part of the body, including sores inside the mouth, vagina, or anus. 

The rash of secondary syphilis is often found on the palms of the hands and the soles of the feet, which is unusual for most rashes. In some people, the rash may be mild and not noticed. Raised gray or whitish patches of skin, known as condyloma lata, may also develop, particularly in warm and moist areas of the body such as the armpits, mouth, or groin.

In secondary syphilis, the infection has spread throughout the body, so other symptoms may be associated with the skin manifestations:

• Fever
• Enlarged lymph nodes
• Fatigue
• Weight loss
• Hair loss
• Headaches
• Muscle aches

These symptoms will eventually subside, but if this secondary stage of the infection is not treated, the infection can progress to tertiary syphilis.

Tertiary syphilis

After the symptoms of secondary syphilis go away, the infection remains latent in the body if untreated. About 15% of infected and untreated people will go on to develop the third stage of syphilis, which can occur as much as 10 to 20 years after the initial infection. Tertiary syphilis is characterized by damage to any number of organ systems and can even be fatal. 

Tertiary syphilis can cause damage to the 

• Brain
• Nerves
• Eyes
• Heart
• Blood vessels
• Liver
• Bones
• Joints

Symptoms that can result from the late stage of syphilis include problems with movement, gradual loss of sight, dementia, paralysis, and numbness. Neurosyphilis is the term used to refer to the involvement of the central nervous system and alterations in neurologic function.

Neonatal or congenital syphilis

Untreated syphilis in pregnant women results in the death of the fetus in up to 40% of infected pregnant women (stillbirth or death shortly after birth), so all pregnant women should be tested for syphilis at their first prenatal visit. The screening test is usually repeated in the third trimester of pregnancy as well. If infected babies are born and survive, they are at risk for serious problems including seizures and developmental delays. Fortunately, syphilis in pregnancy is curable.

There are two types of tests used to diagnose syphilis: treponemal tests (that identify antibodies to the causative organism) and non-treponemal tests (that identify the body's response to the infection but not to the organism itself).

The blood tests used to screen for syphilis are called the Venereal Disease Research Laboratory (VDRL) and Rapid Plasminogen Reagent (RPR) tests. These tests detect the body's response to the infection, but not to the actual Treponema organism. While these are good screening tests, they are not specific enough to establish the diagnosis. These tests can give false-positive results, so a positive screening VDRL or RPR test must be followed by a treponemal test to detect the organism.

A number of different tests are available that detect antibodies to Treponema pallidum bacteria. Examples include the microhemagglutination assay for T. pallidum (MHA-TP) and the fluorescent treponemal antibody absorbed test (FTA-ABS). These tests can confirm the diagnosis of syphilis if a nontreponemal test such as VDRL or RPR is positive.

Penicillin is the treatment of choice for syphilis in all stages. The dose may be one intramuscular injection of long-acting benzathine penicillin G (2.4 million units) or three doses of this drug at weekly intervals, depending on the stage of syphilis, or if the stage is unknown.

While treatment kills the bacteria and prevents further organ damage, it will not reverse damage to the organs that have already occurred. Treatment with penicillin is safe during pregnancy.

As mentioned, untreated syphilis spreads throughout the body and causes complications with various organ systems. Some of the better-known complications of late syphilis include blindness, dementia, aortic aneurysm, deafness, stroke, and other complications related to the spreading of the infection to the brain. Late-stage syphilis can cause fatal complications.

Untreated syphilis in pregnant women results in the death of the fetus in up to 40% of infected pregnant women (stillbirth or death shortly after birth).

There is no vaccine available to prevent syphilis. The use of safe sex practices, including condom use, can only prevent syphilis if the infectious chancre is located in a body area protected by a condom. Washing or douching after sexual activity cannot prevent the infection.

It is not always possible to know whether a sex partner is infected with syphilis because the chancre (ulcer) may be located inside the vagina or rectum.

Neonatal syphilis is preventable by treating the mother early in her pregnancy.