A glutamine insertion in the 1A alpha helical domain of the keratin 4 genein a familial case of White Sponge Nevus

White Sponge Nevus (WSN) is a rare, autosomal dominant disorder that predom inantly affects non-cornified stratified squamous epithelia. Clinically, it is characterized by the presence of soft, white, and "spongy" plaques in t he oral mucosa, The characteristic histopathologic features are epithelial thickening, parakeratosis, and vacuolization of the suprabasal layer of ora l epithelial keratinocytes. Mutations in keratin 4 (K4) and keratin 13 (K13 ) genes have already been demonstrated to be responsible for WSN; the ident ification of new keratin mutations in a stratified squamous epithelia close ly related to epidermis is of relevance for the understanding of the bioche mistry of intermediate filaments, and for genotype phenotype correlations. In this study we investigated a 27-y-old, female Italian patient, affected by white asymptomatic oral plaques. Sequence analysis revealed a 3 bp (ACA) heterozygous insertion localized in the helix initiation motif of the 1A a lpha helical domain of K4. We report this new K4 gene mutation and describe an amino acid insertion, in the 1A domain, responsible for a keratin disea se.