**Core Concept**
Testicular involvement without epididymitis is a feature of certain infectious and inflammatory conditions that directly affect the testis. This phenomenon is often associated with specific pathogens or immune responses that target the testicular parenchyma.

**Why the Correct Answer is Right**
The correct answer is related to the clinical manifestation of mumps orchitis. Mumps virus primarily targets the salivary glands, but in post-pubertal males, it can cause testicular inflammation. This occurs due to the presence of mumps virus in the blood, which then infects the testicular tissue, leading to orchitis. The testis is directly involved, whereas the epididymis is spared.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option might be incorrect, as the specific condition causing testicular involvement without epididymitis is not specified. There are other conditions that can cause testicular inflammation, but they might involve the epididymis as well.
* **Option B:** This option is incorrect because it does not specify the correct condition causing testicular involvement without epididymitis. There are other conditions that can affect the testis, but they might involve the epididymis or have different clinical manifestations.
* **Option C:** This option is incorrect because it does not specify the correct condition causing testicular involvement without epididymitis. Other conditions that can cause testicular inflammation might involve the epididymis or have different clinical manifestations.

**Clinical Pearl / High-Yield Fact**
Mumps orchitis is a well-known complication of mumps infection in post-pubertal males. It is essential to recognize this condition, as it can lead to testicular atrophy and fertility issues.

**Correct Answer: C. Mumps orchitis**