**Core Concept**
The patient in this scenario is presenting with symptoms suggestive of a sexually transmitted infection (STI) that has progressed to a more severe form, involving regional lymphadenopathy, systemic symptoms, and organomegaly. The clinical presentation is characteristic of secondary syphilis, which is a complication of primary syphilis infection.

**Why the Correct Answer is Right**
The correct diagnosis of secondary syphilis is supported by the presence of tender and adherent regional lymph nodes, fever, weight loss, and hepatosplenomegaly. These symptoms occur due to the disseminated nature of the infection, where the spirochete Treponema pallidum spreads to multiple organs and tissues, including the lymph nodes, liver, and spleen. The presence of a small transient genital ulcer 4 weeks after exposure is also consistent with primary syphilis, which is the initial stage of the infection.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is likely a distractor representing a different STI, such as genital herpes. However, the absence of vesicular lesions or a history of recurrent episodes makes this diagnosis less likely.
* **Option B:** This option might represent a diagnosis of lymphogranuloma venereum (LGV), another STI caused by Chlamydia trachomatis. However, LGV typically presents with a painless genital ulcer, followed by regional lymphadenopathy and sometimes systemic symptoms.
* **Option C:** This option is a distractor representing a non-STI diagnosis, such as lymphoma or tuberculosis. However, the context of a recent STI exposure and the presence of systemic symptoms make this diagnosis less likely.

**Clinical Pearl / High-Yield Fact**
The "Rule of 10s" for secondary syphilis includes the following clinical features: 10% of patients with secondary syphilis develop neurological symptoms, 10% develop cardiovascular manifestations, and 10% develop ocular involvement. Additionally, syphilis is a classic example of a "great imitator" disease, where its clinical presentation can mimic many other conditions.

**Correct Answer: B. Lymphogranuloma venereum**