**Core Concept**
Plasma cell balanitis of Zoon is a rare, benign condition of the glans penis characterized by chronic inflammation and immune response, leading to the deposition of hemosiderin in the affected tissue.

**Why the Correct Answer is Right**
Plasma cell balanitis of Zoon (PCBZ) is a condition where the glans penis becomes inflamed, leading to the accumulation of hemosiderin, which is an iron-storage complex. This hemosiderin deposition is responsible for the characteristic 'cayenne pepper' stippling seen in PCBZ. The condition is thought to be an autoimmune response, with plasma cells playing a key role in the inflammation.

**Why Each Wrong Option is Incorrect**
**Option A:** Erythroplasia of Queyrat is a type of carcinoma in situ of the penis, characterized by red, velvety patches, and is not associated with hemosiderin deposition or 'cayenne pepper' stippling.

**Option B:** Paget's disease is a type of intraepithelial adenocarcinoma that can affect the skin, breast, or other organs, but it is not associated with hemosiderin deposition or 'cayenne pepper' stippling.

**Option D:** Metronidazole is an antibiotic used to treat various infections, including those of the skin, but it is not associated with the development of 'cayenne pepper' stippling due to hemosiderin deposition.

**Clinical Pearl / High-Yield Fact**
Plasma cell balanitis of Zoon is a rare condition that should be considered in the differential diagnosis of penile lesions, especially in older men. It is often associated with a history of balanitis or phimosis.

**✓ Correct Answer: C. Plasma cell balanitis of Zoon**