**Core Concept:** Lichen Planus is a chronic, immune-mediated, mucocutaneous disease characterized by flat, lacy, purplish papules on the skin or mucous membranes, with or without hair loss. Lichen planus is a T-cell mediated hypersensitivity reaction.

**Why the Correct Answer is Right:** The correct answer is D. Alopecia areata, also known as spot baldness, is a common autoimmune disorder that causes hair loss. It affects both sexes equally and occurs at any age. Alopecia areata is characterized by sudden, non-scarring hair loss in one or more patches. In this case, the absence of symptoms like erythema, scarring, and scratching indicates alopecia areata as the most likely diagnosis.

**Why Each Wrong Option is Incorrect:**

A. Lichen Planus: The correct answer is D, not C. Lichen planus demonstrates erythema and scarring, which is not present in this case.

B. Psoriasis: Psoriasis is a chronic inflammatory skin disease characterized by red, scaly patches. Unlike alopecia areata, psoriasis is not a non-scarring hair loss disease.

C. Alopecia universalis: Alopecia universalis is the most severe form of alopecia areata, causing complete scalp and body hair loss. In this case, hair loss is limited to the scalp, making alopecia areata a more suitable diagnosis.

**Clinical Pearl:**

Alopecia areata is a common autoimmune disease causing non-scarring hair loss, with varying degrees of involvement. It can affect scalp, eyebrows, beard, or other hair-bearing areas. Treatment options include corticosteroids, immunomodulators, and phototherapy, depending on the severity and course of the disease.

**Correct Answer Explanation:**

D. Alopecia areata is the correct answer because the patient presents with non-scarring hair loss without symptoms of inflammation, erythema, or scarring, which are typical of lichen planus, psoriasis, and alopecia universalis. The absence of these symptoms helps narrow down the diagnosis to alopecia areata.