**Core Concept:** Retinitis Pigmentosa (RP) is a group of inherited retinal diseases that cause progressive damage to the photoreceptor cells, leading to visual impairment and eventual blindness. Fundus examination is an essential tool for diagnosing and monitoring RP progression.

**Why the Correct Answer is Right:** In RP, photoreceptor cells degenerate, leading to a characteristic fundus appearance. The correct answer describes the fundus changes observed in RP.

**Why Each Wrong Option is Incorrect:**
A. RP does not cause a normal appearing fundus (False)
B. RP does not cause a waxy yellow discoloration of the retina (False)
C. RP does not cause a mottled or salt-and-pepper appearance of the retina (False)
D. RP does not cause a thinning of the retinal vessels and optic disc (False)

**Clinical Pearl / High-Yield Fact:** The mottled or salt-and-pepper appearance of the retina, also known as "retinal flecks," is a hallmark feature of Retinitis Pigmentosa. This characteristic fundus appearance helps in diagnosing and monitoring RP progression.

**Correct Answer:** C. Retinitis Pigmentosa causes a mottled or salt-and-pepper appearance of the retina. This fundus finding helps in diagnosing and monitoring the disease progression.