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Syphilis — SCE Infectious Diseases MCQ

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ModerateSTIsSyphilisSCE Infectious Diseases

A 25-year-old man presents to the sexual health clinic with a painless hard ulcer on the glans penis. Dark-field microscopy is not available. RPR is non-reactive and TPHA is non-reactive. He reports the lesion appeared 5 days ago. What is the most appropriate next step?

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Correct answer: D — Treat empirically for primary syphilis and repeat serology in 2–4 weeks

In very early primary syphilis (within the first 1–2 weeks of chancre appearance), both non-treponemal (RPR) and treponemal (TPHA) tests may be negative as the antibody response has not yet developed. The serological window period means early primary syphilis cannot be excluded by negative baseline serology. If dark-field microscopy is unavailable, empirical treatment (Benzathine Penicillin G 2.4 MU IM) should be given based on clinical suspicion, with repeat serology at 2–4 weeks. PCR for T. pallidum from the ulcer, where available, can also be used.

Reference: BASHH 2019 – Syphilis guidelines; WHO 2024 – STI guidelines