Chlamydia trachomatis serovars L1, L2, and L3 are associated with which clinical syndrome?

Explanation

## Chlamydia trachomatis Serovars and Clinical Syndromes **Key Point:** C. trachomatis serovars L1, L2, and L3 (invasive serovars) cause lymphogranuloma venereum (LGV), a systemic sexually transmitted infection with characteristic lymph node involvement. ### Serovar Classification and Clinical Associations | Serovars | Clinical Syndrome | Key Features | |----------|---|---| | **A, B, Ba, C** | Trachoma (chronic keratoconjunctivitis) | Leading cause of preventable blindness worldwide | | **D, E, F, G, H, I, J, K** | Non-gonococcal urethritis (NGU), cervicitis, conjunctivitis | Most common genital chlamydial infections | | **L1, L2, L3** | Lymphogranuloma venereum (LGV) | Invasive, systemic; painful inguinal lymphadenopathy | **High-Yield:** The L serovars (L = invasive/lymphotropic) are more invasive and cause systemic disease with prominent lymph node involvement, unlike the D–K serovars which cause localized genital/ocular disease. ### Lymphogranuloma Venereum (LGV) — Key Features 1. **Primary stage:** Small painless genital ulcer (often goes unnoticed) 2. **Secondary stage:** Painful inguinal lymphadenopathy (buboes), often unilateral 3. **Tertiary stage:** Chronic inflammation → rectal strictures, fistulas, and systemic complications 4. **Diagnosis:** PCR, serology, or clinical presentation 5. **Treatment:** Doxycycline 100 mg BD for 3 weeks (longer than non-LGV chlamydial infections) **Clinical Pearl:** LGV is more common in men who have sex with men (MSM) and can present with rectal symptoms, proctocolitis, and systemic manifestations. The prolonged course and invasive nature distinguish it from other chlamydial infections [cite:Harrison 21e Ch 181].