Onychoschizia: scanning electron microscopy.

The distal ends of the fingernails of four women with onychoschizia were studied with scanning electron microscopy. The dorsal surface and tip of each nail showed horizontal lamellar separations representing single cell layers. Some cleavage lines extended proximally into the nail plate, revealing remarkable sculptured cell surfaces deep within the plate. These observations indicate that the lamellar splitting of onychoschizia occurs between cell layers. This presumably results from repeated trauma to a nail plate with diminished adherence between cell layers, secondary to the dissolution of intercellular cement by detergents and nail polish solvents.