Nikolsky sign
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To check for the presence of certain vesicular/bullous diseases, such as pemphigus and pemphigoid a test can be administered to ascertain the fragility of the epithelial attachment mechanisms.
With the eraser side of a pencil down, the investigator firmly places and pushes the pencil against and into the skin and twists. If the patient in fact has one of a number of vesicular/bullous diseases, he or she will test positive for the Nikolsky sign, and a blister will form within a matter of minutes.
[edit] Histologic Basis for the Sign
The idea behind this test lies in the histologic properties of certain vesicular/bullous diseases. In these diseases, there are defects in the cell-to-cell attachement mechanisms, and even minute amounts of trauma can elicit a clinical response of a blister formation when the cells are manually detached with the forceful turn of the pencil eraser on the skin. In the case of pemphigus, the pencil twist easily rips the spinous cells apart because they possess defective desmosomes, and in the case of pemphigoid, the hemidesmosomes are defective. Within minutes, a blister will form, and this is pathognomonic, or absolutely indicative, of a vesicular/bullous disease.
