A woman with a painless indurated ulcer on the vulva has an RPR titre 1:256. TPHA confirms positivity. CSF examination shows 12 lymphocytes/mm³ and CSF VDRL is reactive. She is pregnant at 16 weeks. The diagnosis and treatment are:

• A Neurosyphilis — aqueous crystalline penicillin G 18–24 MU/day IV for 10–14 days, followed by benzathine penicillin G ✓
• B Secondary syphilis — benzathine penicillin G 2.4 MU IM once
• C Latent syphilis — benzathine penicillin G 2.4 MU IM weekly for 3 weeks
• D Primary syphilis — single-dose azithromycin 2 g

Explanation

CSF VDRL reactivity with CSF pleocytosis confirms neurosyphilis regardless of clinical staging; neurosyphilis requires IV aqueous crystalline penicillin G 3–4 MU every 4 hours (18–24 MU/day) for 10–14 days, followed by benzathine penicillin G 2.4 MU IM weekly × 3 doses. In pregnancy, penicillin is the only proven therapy to prevent congenital syphilis — patients with penicillin allergy must be desensitized. Single-dose azithromycin is inadequate and associated with macrolide resistance. Benzathine penicillin alone does not achieve treponemicidal CSF concentrations.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.