White sponge nevus: case report.

White sponge nevus (WSN) is a rare oral mucosal lesion first described by Cannon in 1935, characterized as benign leukokeratotic lesion of early onset with periods of remission and exacerbation. It is usually asymptomatic, although pruritus, burning, and pain have been reported following irritating stimuli.WSN is inherited as an autosomal dominant trait with wide variability of expression and high penetrance. Instances of de novo mutations also have been reported.-WSN resembles a gray-white spongy plaque, which in full expression may be thick and deeply folded. It most frequently affects the oral mucosa, although the vagina and rectum also may be involved. Histologically, the lesion is confined to the epithelial layer, which appears parakeratotic and acanthotic with pyknotic cell nuclei. Cellular vacuolization may affect all layers of the epithelium or be distributed irregularly.The basement membrane remains intact, although a mild inflammatory reaction may be present in the submucosa. This finding aids in differentiating this lesion from leukoplakia or lichen planus. Differential diagnosis should include pachyonychia congenita, dyskeratosis congenita, hereditary benign intraepithelial dyskeratosis, keratosis follicularis, ichthyosiform dermatoses, hypertrophic lichen planus, leukoplakia, and traumatic keratoses.