- Definition
- A clinical dermatological sign where slight rubbing of the skin results in exfoliation or shearing of the outermost layer.
- Indicates intra-epidermal loss of adhesion.
- Can be elicited on erythematous perilesional skin or normal-appearing skin in active disease.
- Pathophysiology
- Acantholysis: Disruption of intercellular connections (desmosomes) between keratinocytes.
- Result: Structural instability of the epidermis allowing layers to slip past one another.
- Associated Conditions (Nikolsky Positive)
- Pemphigus Vulgaris: Autoantibodies vs. desmogleins. Flaccid bullae.
- Toxic Epidermal Necrolysis (TEN): Severe drug reaction.
- Staphylococcal Scalded Skin Syndrome (SSSS): Exfoliative toxin cleaves desmoglein-1.
- Key Negative Association
- Bullous Pemphigoid: Nikolsky is negative. Autoantibodies vs. hemidesmosomes. Tense bullae.
- The entire epidermis remains intact, resulting in tense bullae that do not rupture easily with pressure.