Nikolsky’s sign refers to the shearing away of the superficial epidermis on gentle lateral pressure to apparently normal skin adjacent to a lesion. 👆
It demonstrates epidermal fragility due to loss of intercellular adhesion between keratinocytes.
Originally described in pemphigus vulgaris but also seen in several other blistering dermatoses.

🔬 Pathophysiology

The mechanism is loss of cohesion within the epidermis leading to intraepidermal splitting.
Acantholysis: Breakdown of desmosomal adhesion (e.g. in pemphigus).
Toxin-mediated cleavage: Exfoliative toxins (e.g. in Staphylococcal Scalded Skin Syndrome, targeting desmoglein-1).
Keratinocyte necrosis/apoptosis: Drug-induced epidermal destruction (e.g. Toxic Epidermal Necrolysis).

⚕️ Conditions with a Positive Nikolsky Sign

Condition	Mechanism	Key Feature
Pemphigus vulgaris / foliaceus	Autoantibodies to Desmoglein 1 and 3 → acantholysis	Flaccid bullae, mucosal involvement, intraepidermal split
Staphylococcal Scalded Skin Syndrome (SSSS)	Staph exfoliative toxin → Desmoglein 1 cleavage	Diffuse erythema and desquamation in infants/children
Toxic Epidermal Necrolysis (TEN)	Drug-induced keratinocyte apoptosis	Widespread epidermal necrosis, mucosal ulceration

❗ False Nikolsky Sign

The false Nikolsky sign is elicited by pulling on the roof of a blister, causing extension of the lesion into surrounding skin. It indicates blister fragility but not true acantholysis (the dermo-epidermal junction remains intact).

Bullous pemphigoid
Epidermolysis bullosa
Cicatricial pemphigoid
Dermatitis herpetiformis
Porphyria cutanea tarda
Bullous SLE

💡 Clinical Importance

Distinguishes pemphigus vulgaris (positive Nikolsky) from bullous pemphigoid (negative/false).
Seen in life-threatening conditions such as TEN and SSSS - both require urgent supportive and intensive care management.
Should be interpreted in context with clinical history, mucosal involvement, and histopathology.

📚 References

🧠 Teaching tip: A “+ Nikolsky sign” means the epidermis is unstable and separates easily - a hallmark of intraepidermal blistering (e.g. pemphigus). A “– Nikolsky sign” indicates subepidermal pathology (e.g. bullous pemphigoid). Always think about the level of blister formation to understand the mechanism. ⚗️

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Nikolsky's sign

🩺 What is Nikolsky’s Sign?

🔬 Pathophysiology

⚕️ Conditions with a Positive Nikolsky Sign

❗ False Nikolsky Sign

💡 Clinical Importance

📚 References

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