**Core Concept**
The patient's symptoms suggest a dermatological condition characterized by itchy, annular, scaly plaques, which is a classic presentation of a chronic inflammatory skin disease. This condition involves an immune-mediated response, leading to epidermal hyperplasia and keratinocyte proliferation.

**Why the Correct Answer is Right**
The most likely diagnosis is **Dermatitis Herpetiformis (DH)**, a cutaneous manifestation of celiac disease. DH is characterized by intensely itchy, blistering skin lesions that typically appear on the extensor surfaces of the elbows, knees, and buttocks. The peripheral extension of the plaques is a hallmark feature of DH. The immune-mediated response in DH involves the deposition of IgA antibodies against tissue transglutaminase (tTG) in the dermal papillae, leading to inflammation and blister formation.

**Why Each Wrong Option is Incorrect**
**Option A:** is incorrect because **Psoriasis** typically presents with erythematous, scaly plaques, but it is less likely to have a peripheral extension pattern.

**Option B:** is incorrect because **Seborrheic dermatitis** presents with a distinctive scaly, erythematous rash, primarily on the scalp, face, and torso, and is not typically associated with peripheral extension.

**Clinical Pearl / High-Yield Fact**
The peripheral extension of the plaques in DH is often accompanied by a "cigarette paper" appearance, where the scaling skin is lifted off the underlying dermis, creating a paper-like texture.

**Correct Answer: D. Dermatitis Herpetiformis**