A 22 year old college going adult has H/o sexual exposure with commercial sex worker, now presenting with painful genital lesions and lymphadenopathy in right inguinal region. What is the diagnosis?
**Core Concept**
The patient's presentation of painful genital lesions and lymphadenopathy following sexual exposure with a commercial sex worker suggests a sexually transmitted infection (STI). The key concept here is the need to consider infections that cause genital lesions and lymphadenopathy, which can be caused by various pathogens.
**Why the Correct Answer is Right**
The patient's symptoms are consistent with primary syphilis, caused by the bacterium *Treponema pallidum*. The painful genital lesions, known as chancres, are a classic presentation of primary syphilis. Lymphadenopathy in the right inguinal region is also a common finding. The infection is typically acquired through direct contact with an infected partner during sexual activity. The presence of a chancre and lymphadenopathy in a patient with a history of sexual exposure to a commercial sex worker supports the diagnosis of primary syphilis.
**Why Each Wrong Option is Incorrect**
**Option A:** Herpes simplex virus (HSV) typically presents with vesicular lesions, not painful genital ulcers. While HSV can cause lymphadenopathy, the presence of a chancre and the patient's history make HSV less likely.
**Option B:** Chlamydia trachomatis can cause lymphogranuloma venereum (LGV), which presents with a painless genital lesion, followed by lymphadenopathy. However, the presence of a painful chancre and the patient's history make LGV less likely.
**Option C:** Human immunodeficiency virus (HIV) can cause a variety of symptoms, including lymphadenopathy, but it does not typically present with painful genital lesions.
**Option D:** Granuloma inguinale (donovanosis) is a bacterial infection that causes genital ulcers, but it is less common and typically presents with painless ulcers.
**Clinical Pearl / High-Yield Fact**
When evaluating a patient with a history of sexual exposure and painful genital lesions, consider primary syphilis as a diagnosis, particularly if the patient presents with a chancre and lymphadenopathy. Remember that the diagnosis of syphilis requires a physical examination, laboratory tests, and a thorough history.
**Correct Answer:** C. Primary syphilis.