A 25-year-old man presents with a painful genital ulcer with undermined edges, a necrotic base, and associated tender inguinal lymphadenopathy ('bubo'). Gram stain of the ulcer exudate shows gram-negative bacilli in a 'school of fish' or 'railroad track' arrangement. What is the diagnosis and treatment of choice?

• A Syphilis; benzathine penicillin G
• B Lymphogranuloma venereum; doxycycline
• C Granuloma inguinale (Donovanosis); doxycycline
• D Chancroid (Haemophilus ducreyi); azithromycin or ceftriaxone ✓

Explanation

Chancroid caused by H. ducreyi presents with a painful, soft, undermined-edge ulcer (unlike the painless syphilitic chancre) and tender suppurative lymphadenopathy. Gram stain shows gram-negative coccobacilli in a characteristic 'school of fish'/'railroad track' pattern (chains of organisms). Treatment: single-dose azithromycin 1g PO or single-dose ceftriaxone 250 mg IM. LGV presents with painless primary lesion then groove sign; Donovanosis with painless granulomatous ulcer and Donovan bodies.

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.