Lymphogranuloma venereum is caused by infection with which organism?

• A. Chlamydia trachomatis
• B. Treponema pallidum
• C. Neisseria gonorrhoeae
• D. Haemophilus ducreyi

Answer: (A)

Lymphogranuloma venereum is caused by Chlamydia trachomatis, specifically the L1 through L3 serovars. This organism is an obligate intracellular bacterium with a developmental cycle that begins as infectious elementary bodies and converts to replicating reticulate bodies inside host cells. In LGV, the infection is invasive, spreading through lymphatic channels to regional lymph nodes and producing painful inguinal or femoral lymphadenopathy and often proctocolitis. This invasive, serovar-specific infection distinguishes LGV from other conditions caused by the same genus or by different organisms.

Other listed pathogens cause different sexually transmitted diseases: Treponema pallidum leads to syphilis with a chancre and systemic features; Neisseria gonorrhoeae causes gonorrhea with urethral or cervical discharge and can disseminate; Haemophilus ducreyi causes chancroid with painful genital ulcers and tender nodes.