Nikolsky sign is seen in?
**Core Concept**
The Nikolsky sign is a clinical dermatological sign that indicates a plane of cleavage within the skin, typically seen in conditions that affect the epidermal-dermal junction. It is a test used to assess the strength of the epidermal-dermal junction. The **Nikolsky sign** is positive when slight rubbing of the skin results in exfoliation of the outer layer.
**Why the Correct Answer is Right**
The correct answer is related to conditions where the epidermal-dermal junction is weakened, such as in **staphylococcal scalded skin syndrome (SSSS)**, **toxic epidermal necrolysis (TEN)**, and **pemphigus vulgaris**. In these conditions, the **autoantibodies** or **exotoxins** disrupt the **desmoglein** proteins that hold the epidermal cells together, leading to a positive Nikolsky sign.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it's not directly related to the Nikolsky sign.
**Option B:** Incorrect as it does not typically demonstrate a positive Nikolsky sign.
**Option C:** Incorrect because, although it involves the skin, it's not characteristically associated with the Nikolsky sign.
**Clinical Pearl / High-Yield Fact**
A positive Nikolsky sign is a critical diagnostic clue for **intraepidermal** or **subepidermal** blisters and can be used to differentiate between various bullous diseases. Remembering the conditions associated with a positive Nikolsky sign can help in quickly narrowing down the differential diagnosis.
**Correct Answer:** D. Pemphigus Vulgaris.