Other than pemphigus, Nikolsky’s sign is positive in:
## **Core Concept**
Nikolsky's sign is a clinical dermatological test used to assess the integrity of the skin's epidermal layer. It involves applying gentle pressure or rubbing on the skin to check for easy separation of the outer layer. This sign is positive in conditions where there is a cleavage within or below the epidermis.
## **Why the Correct Answer is Right**
The correct answer, Staphylococcal Scalded Skin Syndrome (SSSS), is a condition caused by staphylococcal toxins that cleave desmoglein 1, a protein crucial for epidermal cell adhesion. This cleavage leads to intraepidermal separation, specifically just beneath the stratum corneum, making Nikolsky's sign positive. The condition primarily affects infants and young children.
## **Why Each Wrong Option is Incorrect**
- **Option A:** Pemphigus is given as a reference condition where Nikolsky's sign is positive due to autoantibodies against desmogleins, leading to intraepidermal blistering.
- **Option B:** Toxic Epidermal Necrolysis (TEN) is a severe skin condition usually drug-induced, characterized by widespread epidermal necrosis and detachment. While it does involve the epidermis, Nikolsky's sign is not specifically diagnostic here as the primary issue is necrosis rather than the superficial cleavage seen in SSSS or pemphigus.
- **Option C:** Stevens-Johnson Syndrome (SJS) is another severe skin and mucous membrane disorder, often drug-induced, which, like TEN, involves more dermal-epidermal junction disruption and is not primarily characterized by a positive Nikolsky's sign due to superficial epidermal cleavage.
## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that Nikolsky's sign can be positive in conditions with superficial epidermal cleavage, such as pemphigus vulgaris, staphylococcal scalded skin syndrome (SSSS), and toxic epidermal necrolysis (though less specific for the latter). Remembering that SSSS is a classic cause in neonates and young children can help in quickly identifying it as an option.
## **Correct Answer:** D. Staphylococcal Scalded Skin Syndrome.