White sponge naevus with minimal clinical and histological changes: report of three cases

White sponge naevus (WSN) is a rare autosomal dominant disorder that predominantly affects non-cornified stratified squamous epithelia: oral mucosa, oesophagus, anogenital area. It has been shown to be related to keratin defects, because of mutations in the genes encoding mucosal-specific keratins K4 and K13. We illustrate three cases diagnosed as WSN, following the clinical and histological criteria, with unusual appearance. They presented with minimal clinical and histological changes that could be misleading in the diagnosis. The patients showed diffuse irregular plaques with a range of presentations from white to rose coloured mucosae involving the entire oral cavity. In one case the lesion was also present in the vaginal area. The histological findings included epithelial thickening, parakeratosis and extensive vacuolization of the suprabasal keratinocytes, confirming WSN diagnosis. Clinical presentation and histopathology of WSN are discussed in relation to the differential diagnosis of other oral leukokeratoses.