**Core Concept**
Vitiligo is a chronic autoimmune skin disorder characterized by the loss of melanocytes, leading to areas of depigmentation on the skin. This results in the destruction of melanin-producing cells, causing the affected areas to lose their pigment.

**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of vitiligo, which involves the immune system attacking and destroying melanocytes. This process is mediated by T lymphocytes, which recognize melanocytes as foreign and initiate an immune response. The destruction of melanocytes leads to the characteristic loss of skin pigmentation. The correct answer is related to the concept of melanocyte destruction.

**Why Each Wrong Option is Incorrect**
**Option A:** Vitiligo is characterized by an overproduction of melanin. **Incorrect** because vitiligo is actually characterized by the loss of melanocytes, not an overproduction of melanin.

**Option B:** Vitiligo is caused by a viral infection. **Incorrect** because vitiligo is an autoimmune disorder, not caused by a viral infection.

**Option C:** Vitiligo is characterized by an increase in melanocyte proliferation. **Incorrect** because vitiligo is actually characterized by the loss of melanocytes, not an increase in their proliferation.

**Clinical Pearl / High-Yield Fact**
One important aspect of vitiligo is its association with other autoimmune disorders, such as thyroid disease and type 1 diabetes. Patients with vitiligo are at increased risk of developing these conditions, making it essential to screen for them in patients with vitiligo.

**Correct Answer: B. Vitiligo is an autoimmune disorder.**