FFinalistSouthampton · 2027
Sexual health
AKT · Sexual health/Bacterial STIs

Syphilis

Treponema pallidum — spirochaete

Overview

Multistage spirochaetal infection: primary (painless chancre), secondary (systemic rash incl. palms/soles, condylomata lata), latent, and tertiary (gummata, cardiovascular, neurosyphilis). "The great imitator."

Recognise

  • Primary: single PAINLESS, indurated genital ulcer (chancre) + painless local lymphadenopathy
  • Secondary (6–8 wks): symmetrical non-itchy rash incl. PALMS and SOLES, condylomata lata, snail-track oral ulcers, lymphadenopathy
  • Tertiary: gummas, aortic aneurysm/aortitis, neurosyphilis (tabes dorsalis, Argyll Robertson pupil, general paresis)

Red flags

  • Neurosyphilis (ocular/auditory/neurological), congenital syphilis, cardiovascular involvement

Differentials & how to tell them apart

Genital herpesherpes ulcers are MULTIPLE and PAINFUL; chancre is single and painless
Chancroid (H. ducreyi)painful ragged ulcer + painful suppurative nodes (rare in UK)
Behçet / fixed drug eruptionnon-infective ulcers
Pityriasis roseaspares palms/soles; herald patch — secondary syphilis involves palms/soles

Investigations

Serology: treponemal tests (EIA/TPPA — stay positive for life) + non-treponemal (RPR/VDRL — titre tracks activity/treatment). Dark-ground microscopy of chancre exudate. LP if neuro features.

Management

Benzathine penicillin G 2.4 MU IM single dose (early syphilis)

  1. 1Early (primary/secondary/early latent): benzathine penicillin G 2.4 MU IM single dose.Gate: Penicillin allergy → doxycycline 100 mg BD for 14 days (early)
  2. 2Late latent: benzathine penicillin G 2.4 MU IM weekly for 3 weeks (doxycycline 100 mg BD ×28d if allergic).
  3. 3Neurosyphilis: procaine penicillin 1.8–2.4 MU IM OD + probenecid 500 mg QDS for 14 days; steroid cover.
Benzathine penicillin G — first-line all stages; dose/frequency by stage
Doxycycline — penicillin allergy: 100 mg BD (14d early / 28d late)
Procaine penicillin + probenecid — neurosyphilis

Key points

Jarisch–Herxheimer reaction: fever/flu-like hours after first dose (cytokine release from spirochaete death) — warn; steroids for cardiovascular/neuro. Congenital syphilis: antenatal screening; treat the mother.

Monitor & prognosis

RPR/VDRL titre fall (4-fold = adequate response); serological follow-up.

Curable; late complications (cardiovascular, neuro) may be irreversible.

Source: BASHH 2024 (syphilis)