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Syphilis is a sexually transmitted disease caused by the bacteria Treponema pallidum.

• Syphilis can occur in three stages of symptoms, separated by periods of apparent good health.

• It begins with a painless sore at the infection site and, in the second stage, causes a rash, fever, fatigue, and loss of appetite.

• If untreated, syphilis can damage the heart, brain, spinal cord, and other organs.

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• Doctors usually do two types of blood tests—one to screen for and one to confirm the infection.

• Penicillin can eliminate the infection, but people can be reinfected.

In the United States, the annual number of people with symptoms diagnosed for the first time peaked in 1990, when there were about 50,000 cases. Only about 6,000 such cases were reported in 2000, but the number went up to about 9,700 in 2006. Most people with syphilis are men, often homosexual men, living in cities. The percentage of blacks infected is 3 times that of other ethnic or racial groups.

Syphilis causes symptoms in three stages (primary, secondary, and tertiary), separated by periods when no symptoms occur (latent stages).

Syphilis is highly contagious during the primary and secondary stages. Infection is usually spread through sexual contact. A single sexual encounter with a person who has early-stage syphilis results in infection about one third of the time. The bacteria enter the body through mucous membranes, such as those in the vagina or mouth, or through the skin. Within hours, the bacteria reach nearby lymph nodes, then spread throughout the body through the bloodstream.

Syphilis can also be spread in other ways. It can infect a fetus during pregnancy (see Problems in Newborns: Some Infections of Newborns ), causing birth defects and other problems. It can also be spread through contact with skin. However, the bacteria cannot survive long outside the human body.

People with syphilis often have other infections, including other sexually transmitted diseases (STDs).


Each stage of symptoms (primary, secondary, and tertiary) is progressively worse. If not treated, syphilis can persist without symptoms for many years and may damage the heart or brain, possibly leading to death. If detected and treated early, syphilis can be cured, and there is no permanent damage.

Primary Stage: A painless sore (called a chancre) appears at the infection site—typically the penis, vulva, or vagina. A chancre may also appear on the anus, rectum, lips, tongue, throat, cervix, fingers, or other parts of the body. Usually only one chancre develops, but occasionally, several develop. Symptoms usually start 3 to 4 weeks after infection but may start from 1 to 13 weeks later.

The chancre begins as a small red raised area, which soon turns into a painless open, deep sore. The chancre does not bleed and is hard to the touch. Lymph nodes in the groin usually swell and are also painless. About half of infected women and one third of infected men are unaware of the chancre because it causes few symptoms. Chancres in the rectum or mouth, usually occurring in homosexual men, are often unnoticed. The chancre usually heals in 3 to 12 weeks. Then, people appear to be completely healthy.

Secondary Stage: The bacteria spread in the bloodstream, causing a widespread rash, swollen lymph nodes, and, less commonly, symptoms in other organs. The rash typically appears 6 to 12 weeks after infection. About one fourth of infected people still have a chance at this time. Usually, the rash does not itch or hurt. It varies in appearance. Unlike rashes caused by most other diseases, this rash commonly appears on the palms or soles. It may be short-lived or may last for months. Even without treatment, the rash eventually resolves, but it may recur weeks or months later. If a rash develops on the scalp, hair may fall out in patches, making it appear moth-eaten. 

Did You Know...?

• A single sexual encounter with a person who has syphilis results in infection about one third of the time.

• About half of the women and one third of the men who have the initial sore of syphilis do not notice it.

Raised bumps called papules (condylomata lata) may develop in moist areas of the skin, such as the armpits, genital area, and anus. These painful papules are very infectious. They may break open and weep. As they resolve, they flatten and turn a dull pink or gray. Mouth sores develop in more than 80% of people.

Secondary-stage syphilis can cause fever, fatigue, loss of appetite, and weight loss. About 50% of people have enlarged lymph nodes throughout the body, and in about 10%, the eyes become inflamed. About 10% of people have inflamed bones and joints that ache. In some people, the skin and whites of the eyes turn yellow (called jaundice) because hepatitis develops. Some have headaches or problems with hearing or vision because the brain, inner ears, or eyes are infected.

Latent Stage: After the secondary stage, people recover and have no symptoms for a time, which may last from years to decades. During this time, the infection is inactive (latent) and is not contagious. However, the bacteria are still present, and tests for syphilis are positive. The latent stage is classified as early (if the initial infection occurred within the previous 12 months) or late (if the initial infection occurred more than 12 months previously).

Tertiary (Third) Stage: Symptoms range from mild to devastating. Tertiary syphilis has three main forms: benign tertiary syphilis, cardiovascular syphilis, and neurosyphilis.

Benign tertiary syphilis usually develops 3 to 10 yr after the initial infection. It is rare today. Soft, rubbery growths called gummas appear on the skin, most commonly on the scalp, face, upper trunk, and legs. They also often develop in the liver or bones, but they can develop in virtually any organ. They may break down, forming an open sore. If untreated, gummas destroy the tissue around them. In bone, they usually cause deep, penetrating pain. Gummas grow slowly, heal gradually, and leave scars.

Cardiovascular syphilis usually appears 10 to 25 years after the initial infection. The bacteria infect the heart and the blood vessels connected to it, including the aorta (the largest artery in the body). The following may result:

• The wall of the aorta may weaken, forming a bulge (aneurysm). The aneurysm may press on the windpipe or other structures in the chest, causing difficulty breathing, a cough, and hoarseness.

• The valve leading from the heart to the aorta (aortic valve) may leak.

• The arteries that carry blood to the heart (coronary arteries) may narrow.

These problems can cause chest pain, heart failure, and death.

Neurosyphilis (which affects the brain and spinal cord) occurs during the first 5 to 10 years after infection. It develops in about 5% of all people with untreated syphilis. It occurs in the following forms:

Meningovascular: The arteries of the brain or spinal cord become inflamed, causing a chronic form of meningitis. At first, people may have a headache and a stiff neck. They may feel dizzy, have difficulty concentrating and remembering things, and have insomnia. Vision may be blurred. Muscles in the arms, shoulders, and eventually legs may become weak or even paralyzed. This form can cause strokes.

Paretic: This form usually begins when people are in their 40s or 50s. The first symptoms are gradual changes in behavior. For example, people may become less careful about personal hygiene, and their moods may change abruptly. They may become irritable and more and more confused. They may have delusions of grandeur. Headaches, insomnia, difficulty concentrating, poor judgment, and fatigue are common. Tremors may occur in the mouth, tongue, outstretched hands, or whole body. Usually, dementia eventually results.

Tabetic (tabes dorsalis): The spinal cord progressively deteriorates. Symptoms begin gradually, typically with an intense, stabbing pain in the legs that comes and goes irregularly. Walking becomes unsteady. People may feel like they are walking on foam rubber. People usually become thin. Erectile dysfunction is common. Eventually, people have difficulty controlling urination (incontinence) and may become paralyzed.


Health care practitioners suspect primary syphilis if people have a typical chancre. They suspect secondary syphilis if people have a typical rash on the palms and soles. Laboratory tests are needed to confirm the diagnosis.Two types of blood tests are used:

• A screening test, such as the Venereal Disease Research Laboratory (VDRL) or the rapid plasma reagin (RPR) test, is done first. Screening tests are inexpensive and easy to do. But they may need to be repeated because for 3 to 6 weeks after the initial infection, results can be negative even though syphilis is present. Such results are called false-negative. Screening test results are sometimes positive when syphilis is not present (false-positive) because another disorder is present.

• A confirmatory test must usually be done to confirm a positive screening test. This blood test measures antibodies specific to the bacteria that cause syphilis, Treponema pallidum. Results of confirmatory tests may also be false-negative during the first few weeks after initial infections and thus may need to repeated.

Screening test results may become negative after successful treatment, but the confirmatory test results stay positive indefinitely.

In the primary or secondary stages, syphilis may also be diagnosed using darkfield microscopy. A sample of fluid is taken from a skin or mouth sore and examined using a specially equipped light microscope. The bacteria appear bright against a dark background, making them easier to identify.

In the latent stage, antibody tests of blood and spinal fluid are used to diagnose syphilis.

In the tertiary stage, the diagnosis is based on symptoms and antibody test results. Depending on which symptoms are present, other tests are done. For example, a chest x-ray may be taken or another imaging test may be done to check for an aneurysm in the aorta. If neurosyphilis is suspected, a spinal tap (lumbar puncture) is needed to obtain spinal fluid, which is tested for antibodies to the bacteria.


Penicillin given by injection is the best antibiotic for primary, secondary, and early latent syphilis. For primary and secondary stages of syphilis, one dose of long-acting penicillin is all that is needed. However, some people need another dose 1 week later. For late latent stage and some forms of the tertiary stage, three doses are given, separated by 1 week.

If syphilis affects the eyes, inner ears, or brain, penicillin may be given intravenously every 4 hours for 10 to 14 days. People who are allergic to penicillin may be given other antibiotics such as ceftriaxone (given by injection daily for 10 days) or doxycycline (taken by mouth for 14 days).

Because people with primary or secondary syphilis can pass the infection to others, they must avoid sexual contact until they and their sex partners have completed treatment. If people have primary-stage syphilis, all their sex partners of the previous 3 months are at risk of being infected. If they have secondary-stage syphilis, all sex partners of the previous year are at risk. Such sex partners require a blood test for antibodies to the bacteria. If test results are positive, the sex partners need to be treated. Some doctors simply treat all sex partners without waiting for test results.

More than half of people with syphilis in an early stage, especially those with secondary-stage syphilis, develop a reaction 2 to 12 hours after the first treatment. This reaction, called a Jarisch-Herxheimer reaction, causes fever, headache, sweating, shaking chills, and a temporary worsening of the sores caused by syphilis. Doctors sometimes mistake this reaction for an allergic reaction to penicillin. Rarely, people with neurosyphilis have seizures or become paralyzed. Symptoms of this reaction usually subside within 24 hours and rarely cause permanent damage.

After treatment, examinations and blood tests are done periodically until no infection is detected. If treatment of primary, secondary, or latent-stage syphilis is successful, most people have no more symptoms. But treatment of tertiary-stage syphilis cannot reverse any damage done to organs, such as the brain or heart. People with such damage usually do not improve after treatment. People who have been cured of syphilis do not become immune to it and can be infected again.

Resource: Merck Manual Home Edition

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