Introduction
Syphilis is a sexually transmitted infection (STI) caused by a bacterium called Treponema pallidum. It spreads mainly through vaginal, anal or oral sex, kissing or close physical contact with an infected sore. Most infected people do not realize they have the disease and unknowingly pass it to their sexual partners.
Stages of Syphilis
Syphilis develops in three main stages, and the symptoms differ at each stage.
1. Primary Syphilis
- Symptoms appear 10 days to 3 months after exposure.
- Starts with a small, painless sore called a chancre.
- The sore appears where the bacteria entered the body—penis, vagina, anus, rectum, lips or tongue.
- Sore is very infectious but painless, so many people miss it.
- It disappears in 2–6 weeks even without treatment, but the infection continues inside the body.
2. Secondary Syphilis
Begins a few weeks after the primary chancre heals.
- Non-itchy rash on body, especially palms and soles
- Swollen lymph nodes
- Tiredness and headaches
Less common symptoms include:
- Fever
- Weight loss
- Patchy hair loss
- Joint pains
Symptoms may disappear and come back many times. If not treated, the disease enters the latent stage.
Latent Phase
This is the hidden stage where the infected person has no symptoms. They may still be infectious in the first year. After 1–2 years, they may not infect others—but still remain infected.
The latent phase may last for years or even decades.
3. Tertiary Syphilis
About one-third of untreated patients eventually reach this dangerous stage.
It can begin years or decades after initial infection and causes serious damage to the heart, brain, nerves and other organs.
Pathophysiology
Treponema pallidum cannot be easily grown in lab culture; therefore, its exact metabolism and growth features are not fully understood.
Early Local Infection
- The bacteria enter through tiny breaks in the skin during sexual contact.
- They multiply slowly and create the primary chancre (painless ulcer).
- Some bacteria enter nearby lymph nodes and spread throughout the body.
Immune Response
- The initial immune response attracts neutrophils and then T lymphocytes to the infection site.
- Although the immune system helps heal the chancre, the bacteria continue to spread silently.
- The body produces antibodies early in the infection, which are useful for diagnosis.
Causes
- Syphilis is caused by Treponema pallidum.
- Spread through unprotected vaginal, anal or oral sex.
- Spread through contact with an infected syphilis sore.
- Can spread via shared sex toys.
Diagnosis
Physical Examination
- Doctors examine the genital area, mouth and anus for sores.
- Women may need an internal vaginal examination.
Blood Tests
- The body produces antibodies against the bacteria.
- Blood tests detect these antibodies.
- Positive result means current or past infection.
- A negative result early in infection may require repeat testing after 3 months.
- All pregnant women should be screened because syphilis can infect the baby.
VDRL (Venereal Disease Research Laboratory Test)
A screening blood test that detects antibodies produced against T. pallidum. Commonly used worldwide.
Swab Test
A swab taken from an open sore is examined under a microscope or sent to a lab for identification of the bacteria.
Treatment
Syphilis is curable with proper antibiotics. Treatment must be supervised carefully, and long-term follow-up is needed.
First-Line Treatment
- Penicillin G Benzathine 2.4 million units IM as a single dose.
Alternative Option
- Doxycycline 100 mg orally twice daily.
- Prednisone 40–60 mg once daily for 3 days (started 24 hours before penicillin if needed).
Pregnant women with syphilis should be treated immediately to prevent harm to the baby. Newborns may also need antibiotics.
Prevention
- Use condoms during every sexual contact.
- Provide sex education to teenagers.
- Increase awareness among high-risk groups (sex workers, IV drug users, truck drivers, prisoners).
- Avoid sexual contact until sores are fully healed and partners are tested.
- Follow-up blood tests are necessary after treatment.
- Pregnant women should be screened early in pregnancy, and again later if high-risk.
- Testing for other STIs is recommended.
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