Painless ulcer along with painless lymphadenopathy is characteristic of which STD:
**Core Concept**
Lymphogranuloma venereum (LGV) is a sexually transmitted disease caused by specific serovars of Chlamydia trachomatis. It is characterized by a triad of symptoms: painless genital ulcer, painless lymphadenopathy, and eventually, bubo formation.
**Why the Correct Answer is Right**
LGV serovars (L1, L2, and L3) infect the lymphatic system, leading to lymphadenopathy and the characteristic painless ulcer, often referred to as a "primary lesion." The lymph nodes become suppurative, forming buboes, which are painful and tender. The painless nature of the initial ulcer and lymphadenopathy is due to the specific serovars of Chlamydia trachomatis involved in LGV.
**Why Each Wrong Option is Incorrect**
* **Option A:** Syphilis, caused by Treponema pallidum, typically presents with a painless chancre, but it is not associated with painless lymphadenopathy.
* **Option B:** Chancroid, caused by Haemophilus ducreyi, presents with a painful genital ulcer and tender lymphadenopathy, which is opposite to the characteristics of LGV.
* **Option C:** Herpes simplex virus (HSV) typically causes painful genital ulcers and is not associated with painless lymphadenopathy.
**Clinical Pearl / High-Yield Fact**
LGV is often underdiagnosed due to its nonspecific symptoms and the fact that it is a rare disease. Clinicians should consider LGV in the differential diagnosis of genital ulcers and lymphadenopathy in patients with a history of recent sexual exposure.
**Correct Answer:** C.