A 28-year-old man presents with a painless, indurated, clean-based genital ulcer with a rubbery consistency. Inguinal lymphadenopathy is non-tender. Dark-field microscopy of serous fluid from the ulcer base shows actively motile, corkscrew-shaped organisms with characteristic end-flexion movements. Serology: VDRL reactive 1:32, TPHA positive. What is the stage and drug of choice?
- A Secondary syphilis; doxycycline 100 mg twice daily for 14 days
- B Primary syphilis; azithromycin 1 g single oral dose
- C Latent syphilis; benzathine penicillin G 2.4 million units weekly for 3 weeks
- D Primary syphilis; benzathine penicillin G 2.4 million units IM single dose ✓
Explanation
A painless, indurated ulcer (Hunterian chancre) at the site of inoculation with non-tender regional lymphadenopathy represents primary syphilis caused by Treponema pallidum. Dark-field microscopy showing corkscrew-shaped spirochaetes with rotary motility and end-to-end flexion is diagnostic. Treatment for primary, secondary, and early latent syphilis (less than 1 year) is benzathine penicillin G 2.4 million units IM as a single dose. Doxycycline 100 mg twice daily for 14 days is the alternative for penicillin-allergic patients. Azithromycin resistance is emerging and is no longer recommended by most guidelines.
Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.