## Chlamydia trachomatis Serovars and Clinical Syndromes **Key Point:** Serovars D–K of *Chlamydia trachomatis* are the most common cause of genital and urogenital infections worldwide, including cervicitis, urethritis, and pelvic inflammatory disease (PID). ### Serovar Classification by Disease Association | Serovars | Clinical Syndrome | Frequency in Genital Infection | |----------|-------------------|--------------------------------| | A, B, Ba, C | Trachoma (keratoconjunctivitis) | Rare in genital tract | | **D–K** | **Genital/urogenital infection, cervicitis, urethritis, PID** | **Most common (>90%)** | | L1, L2, L3 | Lymphogranuloma venereum (LGV) | Invasive, systemic | | M–U | Non-existent serovars | N/A | **High-Yield:** In routine genital chlamydial infections presenting with cervicitis or urethritis, serovars D–K account for >90% of cases. Serovars A–C cause trachoma (ocular infection in endemic areas) and are rare in genital disease. ### Clinical Pearl Serovars L1, L2, L3 cause lymphogranuloma venereum (LGV), a more invasive syndrome with systemic lymphadenopathy and rectal involvement. These are less common than D–K but are important to recognize because they require prolonged doxycycline therapy (21 days vs. 7 days for non-LGV serovars). ### Pathophysiology Serovars D–K express surface antigens that promote mucosal invasion and intracellular replication in columnar epithelium of the cervix, urethra, and rectum. They do not typically cause systemic dissemination, unlike L serovars. [cite:Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases Ch 175]
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.