What Is Syphilis and How Is It Caused?
Syphilis is a sexually transmitted infection (STI) caused by the spirochete bacterium Treponema pallidum. It is almost always transmitted through:
- Direct sexual contact (vaginal, anal, oral) with infectious lesions
- Mother-to-child during pregnancy or childbirth (congenital syphilis)
- Rarely: blood transfusion or organ transplant (extremely rare with modern screening)
Syphilis is highly contagious during the primary and secondary stages when sores or rashes are present. The bacterium cannot survive long outside the body, so you cannot get syphilis from toilet seats, swimming pools, or shared clothing.
The Four Stages of Syphilis: Detailed Symptoms
Syphilis progresses in four distinct stages if left untreated. Many people have mild or no symptoms and unknowingly spread the disease. The four stages are:
- Primary Syphilis (2–12 weeks after exposure)
The hallmark is a painless ulcer called a chancre (pronounced “shanker”) at the site of infection — usually genitals, anus, rectum, lips, or inside the mouth.
Key features include:
- Single or multiple painless sores
- Round, firm borders with clean base
- Highly infectious
- Heals spontaneously in 3–6 weeks even without treatment
- Swollen lymph nodes nearby
Because Syphilis is painless and often hidden (e.g., cervix, rectum, throat), many people never notice it.
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- Secondary Syphilis (2 weeks–6 months after chancre heals)
Bacteria spread through the bloodstream, causing systemic symptoms:
- Rash — typically on palms and soles (classic but not universal sign), trunk, limbs
- Rough, red or reddish-brown spots
- Non-itchy
- Can be faint and easily missed
- Fever, fatigue, sore throat, weight loss
- Patchy hair loss (“moth-eaten” alopecia)
- Mucous patches in mouth, vagina or anus (grayish, highly contagious)
- Condyloma lata — moist, wart-like lesions in warm, moist areas
All symptoms resolve without treatment, leading to the dangerous latent phase.
- Latent Syphilis (“Hidden Stage”)
No visible symptoms, but infection remains. Divided into:
- Early latent (<12 months) — still infectious
- Late latent (>12 months) — rarely infectious sexually, but can affect pregnancy
Can last years or decades.
- Tertiary (Late) Syphilis (1–30+ years after infection)
Occurs in ~30% of untreated people. Severe, life-threatening damage to:
- Heart and blood vessels (cardiovascular syphilis — aortic aneurysms)
- Brain and nervous system (neurosyphilis — dementia, paralysis, blindness, deafness)
- Bones, skin, internal organs (gummatous syphilis — soft tumor-like growths)
Neurosyphilis, ocular syphilis, and otic syphilis can occur at any stage, even early, and are medical emergencies.
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Congenital Syphilis: A Preventable Tragedy
When a pregnant woman has syphilis, the bacterium can cross the placenta. Consequences include:
- Miscarriage or stillbirth (40% risk)
- Premature birth, low birth weight
- Bone deformities, severe anemia, enlarged liver/spleen, blindness, deafness
- Late manifestations (Hutchinson teeth, saddle nose, saber shins)
The CDC reported a 30% increase in congenital syphilis from 2021 to 2022 alone — entirely preventable with screening and penicillin treatment.
Diagnosis of Syphilis: Two Main Testing Strategies
Because symptoms are so variable (“the great imitator”), laboratory testing is essential.
- Traditional Algorithm
- Nontreponemal tests first (screening): RPR (Rapid Plasma Reagin) or VDRL
- Quantitative titer shows disease activity
- Can become negative after successful treatment
- Positive screening → confirmatory treponemal test (TP-PA, FTA-ABS, or EIA/CIA)
- Reverse Algorithm (increasingly common)
- Treponemal test first (EIA/CIA) → if positive → RPR → if discordant → TP-PA
Special situations:
- Neurosyphilis: Lumbar puncture if neurologic symptoms
- Pregnancy: Test at first prenatal visit, third trimester, and delivery in high-risk areas
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Treatment of Syphilis:
Syphilis is 100% curable with appropriate antibiotics if caught early. The earlier, the better. The table below shows recommended treatment for syphilis based on the different stages:
| Stage | Recommended Treatment (CDC 2021 Guidelines, reaffirmed 2025) | Follow-up |
| Primary, Secondary, Early Latent | Benzathine penicillin G 2.4 million units IM, single dose | RPR at 6 & 12 months |
| Late Latent, Unknown Duration | Benzathine penicillin G 2.4 million units IM weekly × 3 doses (total 7.2 million units) | RPR at 6, 12, 24 months |
| Neurosyphilis, Ocular, Otic | Aqueous crystalline penicillin G 18–24 million units/day IV × 10–14 days ± benzathine penicillin weekly × 3 | LP repeat every 6 months until CSF normal |
| Pregnancy | Penicillin only — dosing same as non-pregnant by stage; desensitize if allergic | Monthly testing; sonogram at ≥20 weeks |
| Penicillin Allergy | Desensitization in hospital (preferred) or doxycycline (non-pregnant only) | Same serologic follow-up |
Prevention: How to Protect Yourself and Others against Syphilis
- Consistent condom use — reduces but does not eliminate risk (sores on areas not covered)
- Regular testing — especially if multiple partners, MSM, pregnant, or HIV-positive
- Partner notification & treatment — all sexual contacts within 90 days (primary/secondary) should be treated presumptively
- DoxyPEP (post-exposure prophylaxis) — emerging data show 200 mg doxycycline within 72 hours of condomless sex reduces syphilis by ~87% in high-risk groups (CDC is considering formal recommendation in 2025)
- PrEP & HIV care — syphilis increases HIV transmission 2–5 fold
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Syphilis has been called “the great imitator” because it mimics so many other diseases — but it is not mysterious. With a single shot of penicillin in early stages, it is completely curable. However, if left untreated, it can destroy one’s life.
Take control:
- Get tested regularly if at risk
- Insist on prenatal screening
- Notify partners if diagnosed
- Use protection and consider DoxyPEP if high-risk
Early detection saves lives. If you have any doubt — test.
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