Nikolsky's sign is associated with which condition?

• A. Basal cell carcinoma
• B. Pemphigus vulgaris
• C. Urticaria
• D. Erythema multiforme

Answer: (B)

Nikolsky's sign shows that the epidermis is unusually fragile and can be pulled away with gentle pressure because cell-to-cell adhesion in the epidermis is disrupted. This happens prominently in pemphigus vulgaris, where autoantibodies attack desmoglein proteins in desmosomes, causing acantholysis and the formation of intraepidermal blisters. When you apply lateral pressure, the intact roof of the blister easily displaces, revealing the sign. The other conditions listed don’t involve this specific autoimmune loss of cell adhesion in the epidermis—basal cell carcinoma is a malignant skin tumor, urticaria involves superficial dermal edema with transient wheals, and erythema multiforme presents with target lesions and mucosal involvement but not the acantholysis seen in pemphigus vulgaris.