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Syphilis and sexually transmitted infections
Syphilis is diagnosed with a non-treponemal test (VDRL or RPR, its titre followed) together with a treponemal test, and treated with benzathine penicillin G 2.4 million units intramuscularly — one dose in early syphilis and three weekly doses in late syphilis; in every sexually transmitted infection HIV is tested and the partner treated.
Why it matters in the exam
The question presents a painless genital ulcer (primary syphilis), or a rash that includes the palms and soles, mucosal lesions and nodes (secondary syphilis). Remember that the non-treponemal test (RPR) is also used for follow-up — a 4-fold fall in titre shows response — while the treponemal test stays positive for life. Early syphilis (primary, secondary and latent under one year) is treated with a single dose; late or unknown latent — three doses a week apart. Neurosyphilis, which can occur at any stage (eyes, ears, mental change), is treated with intravenous penicillin for 10–14 days.
In pregnancy only penicillin is used — with desensitisation for allergy — because only it prevents congenital syphilis. After the first treatment a Jarisch-Herxheimer reaction may occur: fever, chills and muscle aches within hours, treated with support only. Other sexually transmitted infections: gonorrhoea — ceftriaxone 500 mg intramuscularly as a single dose; chlamydia — doxycycline 100 mg twice a day for 7 days (azithromycin in pregnancy). With every diagnosis of a sexually transmitted infection, HIV, syphilis and hepatitis are tested and partners are treated. Pelvic inflammatory disease is covered in the gynaecology chapter.
Key points
- Diagnosis: RPR or VDRL + treponemal test; follow-up with RPR.
- Early: benzathine penicillin G 2.4 million units, one dose; late: 3 doses.
- Neurosyphilis: intravenous penicillin for 10–14 days.
- Pregnancy: penicillin only, with desensitisation for allergy.
- Gonorrhoea: ceftriaxone 500 mg; chlamydia: doxycycline for 7 days; HIV and partners for all.
Summary table
| Stage / infection | Presentation | Test | Treatment |
|---|---|---|---|
| Primary syphilis | Painless ulcer (chancre) | RPR or VDRL + treponemal test | Benzathine penicillin G 2.4 million units IM, one dose |
| Secondary syphilis | Rash including palms and soles, mucosal lesions | As above; high titre | One dose |
| Late or unknown latent | No symptoms, over a year | Serology only | 3 doses a week apart |
| Neurosyphilis | Eyes, ears, mental change — at any stage | Lumbar puncture | Intravenous penicillin for 10–14 days |
| Gonorrhoea | Urethral or cervical discharge | NAAT | Ceftriaxone 500 mg IM, single dose |
| Chlamydia | Discharge, often no symptoms | NAAT | Doxycycline 100 mg twice a day for 7 days; azithromycin in pregnancy |
Free exam questions
תסנין דיפוזי עם דומיננטיות/הרבה תאי פלזמה תמצא ב: (the question as examined, in Hebrew)
- א. SYPHILIS שלישוני
- ב. HISTOPLASMOSIS
- ג. ANAPLASTIC LARGE CELL LYMPHOMA
- ד. BOWEL BYPASS SYNDROME
אילו מהמשפטים הבאים אינו נכון בנוגע למחלת העגבת: (the question as examined, in Hebrew)
- א. Treponema pallidum הינה מחולל מחלה בבני אנוש בלבד
- ב. Treponema pallidum עשוי לעבור דרך נשאים אסימפטומטיים
- ג. קיימת עמידות כנגד מקרולידים
- ד. קווינולונים אינם טיפול מומלץ
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Sources
- CDC Sexually Transmitted Infections Treatment Guidelines, 2021 — Syphilis, gonorrhoea and chlamydia
- Harrison's Principles of Internal Medicine, 21st edition (2022) — Syphilis; Gonococcal Infections; Chlamydial Infections
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.