**Core Concept**
Pellagra is a disease caused by niacin (vitamin B3) deficiency, which affects the skin, mucous membranes, and the nervous system. The characteristic skin lesions in pellagra are a result of impaired niacin metabolism, leading to increased levels of toxic compounds.

**Why the Correct Answer is Right**
The appearance seen in pellagra is known as **Dermatitis Dieta** or **Casal's necklace**. This condition occurs due to the accumulation of niacin deficiency-related toxins, such as tryptophan metabolites, which cause inflammation and damage to the skin. The lesions are typically found on sun-exposed areas, like the face, neck, and hands.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Dermatitis Dieta is a specific type of skin lesion associated with pellagra, whereas dermatitis herpetiformis is a different condition characterized by intensely itchy, blistering skin.
**Option B:** This option is incorrect because seborrheic dermatitis is a common skin condition, but it is not specifically associated with pellagra or niacin deficiency.
**Option C:** This option is incorrect because psoriasis is an autoimmune condition that causes thick, scaly skin patches, but it is not related to niacin deficiency or pellagra.

**Clinical Pearl / High-Yield Fact**
Remember that pellagra is a classic example of a **nutritional deficiency disease**, and it can be prevented by a balanced diet rich in niacin or vitamin B3.

**Correct Answer:** C.