LGV is caused by
**Core Concept**
Lymphogranuloma venereum (LGV) is a sexually transmitted infection caused by specific serovars of Chlamydia trachomatis. It primarily affects the lymphatic system, leading to inflammation and swelling of the lymph nodes.
**Why the Correct Answer is Right**
The correct answer is Chlamydia trachomatis serovars L1-L3. LGV is characterized by the invasion of Chlamydia trachomatis serovars L1-L3 into the lymphoid cells, leading to an immune response and subsequent inflammation. This results in the formation of buboes, which are painful and swollen lymph nodes in the groin area. The pathogenesis of LGV involves the chlamydial inclusion bodies, which are formed within the cytoplasm of infected cells.
**Why Each Wrong Option is Incorrect**
**Option A:** The correct answer is not Treponema pallidum, as it is the causative agent of syphilis, a different sexually transmitted infection.
**Option B:** The correct answer is not Haemophilus ducreyi, as it is the causative agent of chancroid, another sexually transmitted infection that presents with painful ulcers.
**Option C:** The correct answer is not Neisseria gonorrhoeae, as it is the causative agent of gonorrhea, a sexually transmitted infection that can cause urethritis, cervicitis, and pelvic inflammatory disease.
**Clinical Pearl / High-Yield Fact**
LGV is often asymptomatic in its initial stage, making it difficult to diagnose. However, the presence of painful lymphadenopathy and buboes is a classic clinical feature of the disease.
**Correct Answer: C. Chlamydia trachomatis serovars L1-L3.**