A couple, who did not know each other very well, dated and had sexual contact. Several weeks later, the man noticed a small, painless vesicle on his penis, which ruptured and then healed. Soon, his inguinal lymph nodes enlarged and discharged pus through multiple sinus tracts. Lymphogranuloma venereum (LGV) is a venereal disease caused by serotype L1, L2, or L3 of Chlamydia trachomatis. The differential diagnosis should include which of the following?

**Core Concept**
Lymphogranuloma venereum (LGV) is a sexually transmitted infection (STI) caused by specific serovars (L1, L2, or L3) of Chlamydia trachomatis, characterized by a triad of symptoms: a painless primary lesion, enlarged inguinal lymph nodes, and lymphadenopathy with fistula formation.

**Why the Correct Answer is Right**
The correct answer is a condition with similar clinical manifestations to LGV. The key features of the correct answer are the presence of a painless genital lesion, followed by lymphadenopathy and fistula formation. This clinical presentation is consistent with the characteristic triad of LGV. The correct answer is also a sexually transmitted infection, which aligns with the mode of transmission of LGV.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not closely match the clinical presentation of LGV. The primary lesion in LGV is typically painless and heals without scarring, whereas the primary lesion in this option is painful and may leave a scar.
**Option B:** This option is incorrect because it is not a sexually transmitted infection, unlike LGV. The clinical presentation of this option does not closely match the triad of symptoms associated with LGV.
**Option C:** This option is incorrect because it is not a sexually transmitted infection and does not have a similar clinical presentation to LGV.

**Clinical Pearl / High-Yield Fact**
LGV is a clinical diagnosis based on the characteristic triad of symptoms, and laboratory confirmation is often delayed due to the non-specific nature of the tests. A high index of suspicion and thorough clinical evaluation are essential for diagnosing LGV.

**Correct Answer:** D.

✓ Correct Answer: B. Chancroid