White Sponge Nevus

White sponge nevus (WSN) is a rare autosomal dominant disorder with a high degree of penetrance and variable expressivity; it predominantly affects noncornified stratified squamous epithelium.The disease usually involves the oral mucosa and (less frequently) the mucous membranes of the nose, esophagus, genitalia, and rectum.The lesions of WSN may be present at birth or may first manifest or become more intense at puberty.
Genetic analyses of families with WSN have identified a missense mutation in one allele of keratin 13 that leads to proline substitution for leucine within the keratin gene cluster on chromosome 17.A new study, using sequence analysis, has reported a  glutamine insertion localized in the helix initiation motif of the 1A alpha helical domain of Keratin 4 gene.


FEATURES
White sponge nevus presents as bilateral symmetric white, soft, “spongy,” or velvety thick plaques of the buccal mucosa. However, other sites in the oral cavity may be involved, including the ventral tongue, floor of the mouth, labial mucosa, soft palate, and alveolar mucosa. The condition is usually asymptomatic and does not exhibit tendencies toward malignant change. The characteristic histopathologic features are epithelial thickening, parakeratosis, a peculiar perinuclear condensation of the cytoplasm, and vacuolization of the suprabasal layer of keratinocytes. Electron microscopy of exfoliated cells shows numerous cellular granules composed of disordered aggregates of tonofilaments.
DIFFERENTIAL DIAGNOSIS

The lesions of WSN may be grossly similar to those of other hereditary mucosal syndromes such as hereditary benign intraepithelial dyskeratosis or pachyonychia congenita, infections such as candidiasis, traumatic lesions seen in cheek chewing, and chemical burns or preneoplastic/neoplastic processes.

This differential diagnosis is best resolved in many cases by incisional biopsy specimens interpreted in the context of the clinical history and physical findings.
TREATMENT

No treatment is indicated for this benign and asymptomatic condition. Patients may require palliative treatment if the condition is symptomatic. One study has reported some relief of symptoms with a tetracycline rinse.