**Question:** On membrane removal of a lesion, Sign (Arrows) seen in Psoriasis

**Core Concept:** Psoriasis is a chronic inflammatory skin disorder characterized by hyperproliferation of keratinocytes, resulting in erythema, scaling, and plaque formation. The histopathological changes in psoriasis involve the epidermis and dermis.

**Why the Correct Answer is Right:** In psoriasis, the removal of the epidermal cell layer (membrane) reveals the Psoriatic Arrows sign. This sign is characterized by the presence of thickened, irregular, and elongated dermal papillae extending into the epidermis. These papillae are associated with a dense inflammatory infiltrate composed of lymphocytes, histiocytes, and plasma cells. This sign is suggestive of psoriasis and helps differentiate it from other skin conditions with similar features.

**Why Each Wrong Option is Incorrect:**

A. **Psoriasis Arrows:** This is not a correct term for the sign seen in psoriasis. The correct term is Psoriatic Arrows.
B. **Diploid cells:** Diploid cells are normal cells with a diploid number of chromosomes. In psoriasis, the Psoriatic Arrows sign is observed, not the presence of diploid cells.
C. **Inflammatory infiltrate:** While the presence of an inflammatory infiltrate is a feature of psoriasis, this option is too vague and does not specifically address the sign observed.
D. **Epidermal hyperplasia:** While epidermal hyperplasia is a general feature of psoriasis, it does not describe the specific sign observed with the Psoriatic Arrows.

**Clinical Pearl:** The Psoriatic Arrows sign, also known as the Munro's sign, is a key feature in the diagnosis of psoriasis. It is observed on membrane removal, revealing dermal papillae extending into the epidermis with a dense inflammatory infiltrate. This sign helps differentiate psoriasis from other skin conditions with similar features, such as eczema or lichen planus.

**Correct Answer:** D. Psoriatic Arrows (Munro's sign)

**Explanation:**

Psoriatic Arrows (Munro's sign) is a crucial diagnostic clue in psoriasis. When the epidermal cell layer is removed, the following features are observed:

1. Thickened, irregular, and elongated dermal papillae extending into the epidermis.
2. A dense inflammatory infiltrate composed of lymphocytes, histiocytes, and plasma cells.

This sign provides essential information for distinguishing psoriasis from other skin conditions that share similar clinical features, such as eczema or lichen planus. By understanding and recognizing this sign, physicians can make an accurate diagnosis and provide appropriate treatment for the patient.