**Core Concept**
Vogt-Koyanagi-Harada (VKH) syndrome is a rare, multisystem autoimmune disorder characterized by inflammation and damage to pigmented tissues throughout the body, including the eyes, skin, and nervous system. This condition is often associated with a complex interplay between immune system dysregulation and genetic predisposition.

**Why the Correct Answer is Right**
VKH syndrome primarily manifests as a form of uveitis, a type of eye inflammation that affects the uveal tract, which includes the iris, choroid, and ciliary body. The inflammatory response in VKH syndrome is thought to be triggered by an autoimmune response against melanin-containing cells, leading to the characteristic symptoms of uveitis, including eye pain, redness, and vision loss. The involvement of the uveal tract is a hallmark of VKH syndrome, making uveitis the correct answer.

**Why Each Wrong Option is Incorrect**
**Option A:** Cataract is a type of opacification in the lens of the eye that can cause vision loss, but it is not a primary feature of VKH syndrome. While patients with VKH may develop cataracts as a complication, it is not a defining characteristic of the condition.
**Option B:** CNS tumor is not directly related to VKH syndrome. Although patients with VKH may experience neurological symptoms such as headache, meningismus, or cranial nerve palsies, these symptoms are typically secondary to the inflammatory response and not indicative of a primary CNS tumor.
**Option D:** Polycystic kidney disease is a distinct genetic disorder characterized by the growth of numerous cysts on the kidneys, leading to kidney damage and failure. This condition is not associated with VKH syndrome.

**Clinical Pearl / High-Yield Fact**
VKH syndrome is often associated with a characteristic "salt-and-pepper" pigmentation of the hair and skin, which is a result of the autoimmune response against melanin-containing cells. This distinctive skin and hair pattern can be a helpful diagnostic clue in patients presenting with symptoms of VKH syndrome.

**✓ Correct Answer: C. Uveitis**