White sponge nevus (leukoedema exfoliativum mucosae oris): ultrastructural observations.

Biopsy specimens from the oral lesions of white sponge nevus (WSN) in thirteen patients were analyzed by electron microscopy. Several marked deviations from the normal ultrastructure were recorded. Similarities and dissimilarities with other hereditary disturbances affecting the epithelium are discussed. Profound disturbance of the tonofilament system, with atypical aggregation of tonofilaments, was observed. Odland bodies, which are numerous in keratinized epithelia and are extruded into the intercellular space prior to the exfoliation of the surface cells, were also abundant in the WSN specimens. Very little material originating from Odland bodies appears, however, in the intercellular space in WSN. Presumably, the Odland bodies fail to properly function enzymatically in WSN.