**Question:** Differential diagnosis of rosacea includes all of the following except?

A. Eczema
B. Psoriasis
C. Acne vulgaris
D. Lichen planus

**Core Concept:** Rosacea is a chronic inflammatory skin disorder characterized by facial flushing, redness, and papules. Rosacea is often confused with other dermatological conditions like eczema, psoriasis, acne vulgaris, and lichen planus.

**Why the Correct Answer is Right:** Lichen planus is a dermatological condition characterized by flat, papules, and plaques with a characteristic "target-like" appearance. While rosacea may present with papules and redness, its clinical features are distinct from lichen planus. Lichen planus is a systemic disease affecting internal organs as well, unlike rosacea.

**Why Each Wrong Option is Incorrect:**

A. Eczema: Eczema is an allergic skin disorder, typically affecting the flexural areas, and presents with itching, scaling, and oozing rather than facial flushing and papules seen in rosacea.

B. Psoriasis: Psoriasis is a chronic inflammatory skin condition characterized by raised, scaly patches with a silvery-white appearance, whereas rosacea presents as facial flushing, papules, and redness.

C. Acne vulgaris: Acne vulgaris is a condition characterized by comedones, papules, and pustules, primarily affecting the face, chest, and back, while rosacea presents with facial flushing, papules, and redness.

D. Lichen planus: As mentioned earlier, lichen planus presents with flat, papules, and plaques, while rosacea shows facial flushing, papules, and redness.

**Clinical Pearl:** It is essential to differentiate between rosacea and these conditions as they have different management strategies and prognosis. Rosacea is usually managed with topical and systemic antibiotics, while eczema, psoriasis, and acne vulgaris require specific treatment plans targeting their respective features.

**Correct Answer:** Lichen planus (D) is a wrong choice as it has distinct clinical features different from rosacea.

By understanding the unique clinical features of each condition, clinicians can accurately diagnose and manage patients with these dermatological disorders effectively. Differentiating between these conditions is crucial for appropriate treatment and patient management.