Conditions · Systemic conditions
Syphilis !
Syphilis is a sexually transmitted bacterial infection that advances in stages over years and can affect almost any organ; it can pass to the baby in pregnancy.
Updated 2026-10-30
Structures involved
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Microorganisms that cause it
In embryology
In the clinical exam
- Romberg test
- Pupils: light reflex and abnormal pupils (Marcus Gunn, Horner, Argyll Robertson)
- Meningeal syndrome
Why it happens
- Chronic inflammation: causes, cells and features
- Fetal hydrops: immune and nonimmune
- Granulomatous inflammation: caseating vs non-caseating, the causes to know
- Special stains in diagnosis: Congo red, Prussian blue, PAS, Ziehl–Neelsen, Gram
- Blood vessels: artery, vein and capillary layers
What it is
A sexually transmitted infection caused by Treponema pallidum that progresses through stages over years and can affect almost any organ. It can also pass from mother to fetus (congenital syphilis).
Who gets it
Cases have risen again in many countries. In Colombia and Latin America, gestational and congenital syphilis remain priorities, with prenatal rapid-test screening. In a 2013–2014 Lima, Peru, cohort at high risk, recently acquired syphilis was found at baseline in 16.8% of men who have sex with men and 6.7% of transgender women.
Causes
- Treponema pallidum subspecies pallidum, a spirochaete
- Sexual contact (vaginal, anal or oral) with an active lesion
- Transplacental transmission during pregnancy or contact at birth
- Rarely blood transfusion
Risk factors
- Unprotected sex and multiple or new sexual partners
- Men who have sex with men
- HIV infection or other sexually transmitted infections
- Sex work and substance use
- Lack of or late prenatal care (congenital syphilis)
Pathophysiology
Treponemes enter through mucosa or broken skin, multiply locally to form a painless chancre and spread early through lymph and blood. The immune response causes endarteritis of small vessels, which explains most lesions. Without treatment the infection becomes latent, and years later can cause gummas, aortitis or neurosyphilis; the nervous system can be invaded at any stage.
Classification
- Primary: chancre and regional lymphadenopathy
- Secondary: rash, mucocutaneous lesions and systemic symptoms
- Latent: no symptoms, positive serology; early latent (within about a year) or late latent
- Tertiary: gummas, cardiovascular syphilis and late neurosyphilis
- Neurosyphilis, ocular and otic syphilis (can occur at any stage)
- Congenital syphilis: early and late
Symptoms and signs
- Primary: a painless, firm, clean-based ulcer (chancre) on the genitals, anus or mouth, with firm painless inguinal nodes
- Secondary: non-itchy rash including the palms and soles, fever, malaise and generalised lymphadenopathy
- Secondary: condylomata lata (moist genital plaques), mucous patches in the mouth, patchy hair loss
- Neurosyphilis: headache, meningitis, stroke, cognitive decline, unsteady gait, Argyll Robertson pupils
- Ocular or otic: blurred vision, eye pain, hearing loss or tinnitus
- Tertiary: gummas in skin, bone or organs; aortic regurgitation or aneurysm of the ascending aorta
Diagnosis
- Clinical
- Sexual history and full skin, mucosal, genital and lymph-node examination. Screening of all pregnant women and of people at higher risk.
- Tests
- Two types of serology are combined: non-treponemal tests (VDRL, RPR), whose titres reflect activity and response to treatment, and treponemal tests (TPPA, FTA-ABS, EIA, rapid tests), which usually stay positive for life. Lesion PCR or dark-field microscopy; CSF analysis when neurosyphilis is suspected. HIV testing.
- Imaging
- Not routine. Echocardiography or CT angiography for suspected cardiovascular syphilis; brain imaging for neurological signs; long-bone X-rays in congenital syphilis.
Differential diagnosis
- Genital herpes
- Chancroid
- Lymphogranuloma venereum
- Pityriasis rosea or drug eruption (secondary rash)
- Viral exanthems and acute HIV infection
Goal of treatment
Cure the infection, prevent late complications and congenital syphilis, and break the chain of transmission by treating sexual partners.
Treatment
- Medical
- Penicillin is the treatment of choice: long-acting intramuscular benzathine penicillin for primary, secondary and latent syphilis, with the number of doses depending on stage.
- Medical
- Neurosyphilis and ocular or otic syphilis: intravenous penicillin in hospital.
- Medical
- In pregnancy penicillin is the only treatment considered adequate to prevent congenital syphilis; allergic patients are desensitised. Non-pregnant allergic patients may receive tetracyclines.
- Follow-up
- Repeat non-treponemal titres at set intervals to confirm response; warn about the Jarisch–Herxheimer reaction (fever and malaise in the first day).
- Lifestyle
- Notification, testing and treatment of sexual partners, condom use and screening for HIV and other STIs.
Drugs for this condition
- Benzathine benzylpenicillin
- Procaine benzylpenicillin
- Doxycycline
- Tetracycline
- Benzylpenicillin (penicillin G)
Complications
- Neurosyphilis: tabes dorsalis, general paresis, stroke
- Vision and hearing loss
- Syphilitic aortitis with aortic regurgitation or aneurysm
- Gummas destroying bone, skin or organs
- Miscarriage, stillbirth, prematurity and congenital syphilis
- Increased risk of acquiring and transmitting HIV
Prognosis
Early syphilis is cured with penicillin and usually leaves no damage. Late complications such as neurological or cardiovascular damage may be permanent even after cure. Reinfection is possible because infection does not give lasting immunity.
Prevention
- Condom use and partner reduction
- Screening in early pregnancy and repeated later in pregnancy according to national guidelines
- Prompt treatment of pregnant women and their partners
- Screening of people at higher risk and of blood donors
Test yourself
Think of the answer, then tap the question to see it.
What is the typical lesion of primary syphilis?
A painless, indurated, clean-based ulcer (chancre) at the inoculation site, with painless regional lymphadenopathy.
What is the difference between treponemal and non-treponemal tests in syphilis?
Non-treponemal tests (VDRL, RPR) give titres that track activity and treatment response; treponemal tests usually stay positive for life.
Which finding on the palms and soles suggests secondary syphilis?
A non-itchy macular or papular rash involving the palms and soles.
What is the only treatment considered adequate for syphilis in pregnancy?
Penicillin; women allergic to penicillin are desensitised so they can receive it.
What is the Jarisch–Herxheimer reaction?
Fever, chills and malaise within hours of starting treatment, caused by the release of products from dying spirochaetes.
Related conditions
- HIV infection and AIDS
- Aortic Valve Stenosis
- Uveitis
- Human papillomavirus (HPV) infection
- Gonorrhoea
- Chlamydia infection
- Aortic regurgitation
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Syphilis (StatPearls (NCBI Bookshelf), 2024); The PICASSO Cohort: baseline characteristics of a cohort of men who have sex with men and male-to-female transgender women at high risk for syphilis infection in Lima, Peru (BMC infectious diseases, 2017) · adapted, CC BY 4.0.
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