Witkop or Von Sallman-Witkop hereditary benign intraepithelial dyskeratosis is an hereditary, autosomal dominant process with incomplete penetrance.  The mucosa of the mouth and the bulbar conjunctiva are affected.  Orally the lesions are localized at the commisures, buccal mucosa and lips.  The buccal mucosa is affected symmetrically.  The lesion acquires a thick, whitish, spongy, macerated aspect with or without folds, resembling the white sponge nevus.  Thickening increases with age until puberty.  Histology differentiates it from the white sponge nevus. (courtesy of Dr. Eugenio Borello)