A 30-year-old man presents with a painless genital ulcer and large unilateral inguinal lymphadenopathy with groove sign. Frei test is positive. The causative organism type (serovars) is:
- A Chlamydia trachomatis serovars L1, L2, L3 ✓
- B Chlamydia trachomatis serovars A–C
- C Chlamydia trachomatis serovars D–K
- D Chlamydia pneumoniae TWAR strains
Correct answer: A. Chlamydia trachomatis serovars L1, L2, L3
Explanation
Lymphogranuloma venereum (LGV) is caused by Chlamydia trachomatis serovars L1, L2, and L3 (invasive serovars that can penetrate macrophages and spread to lymph nodes). Serovars A-C cause trachoma (ocular disease); serovars D-K cause genital chlamydiosis and non-gonococcal urethritis. Frei test (intradermal LGV antigen) is positive in LGV but is now obsolete. The groove sign (inguinal ligament groove between matted nodes) is pathognomonic.
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.