White sponge nevus WSN, is an autosomal dominant, condition of the oral mucosa (the mucous membrane lining of the mouth). It is caused by a mutations in certain genes coding for keratin, which causes a defect in the normal process of keratinization of the mucosa. This results in lesions which are thick, white and velvety on the inside of the cheeks within the mouth. Usually, these lesions are present from birth or develop during childhood. The condition is entirely harmless, and no treatment is required.<br />Typical main clinical features: White persistent lesions in mouth, rectum, vagina. <br />Diagnosis: Clinical + family history. <br />Investigations: +- Biopsy. <br />Management: Reassurance.