Identification of two novel mutations in keratin 13 as the cause of white sponge naevus.

BACKGROUND

White sponge naevus (WSN) is a rare autosomal dominant condition which is characterised by benign, white spongy plaques (oral leukokeratoses) affecting non-cornifying, wet mucosa. WSN shares several ultrastructural characteristics (eg, epithelial thickening, acanthosis, keratin filament aggregation) with a number of epithelial disorders caused by mutations in keratin genes and to-date two mutations, one in each of the mucosal specific keratins, K4 and K13, have been identified as the molecular basis of the disorder.

OBJECTIVES

To identify the molecular basis of WSN in two families with a history of the disease.

RESULTS

Two novel mutations were identified in helix initiation motif of K13. A T-to-C transition was found in the affected members of one family which is predicted to change leucine115 to proline. In the second family, a similar T-to-C transition was found in codon 108 which is predicted to change methionine to threonine in the protein sequence. These changes were not found in 50 unrelated, unaffected individuals.

CONCLUSIONS

The mutations in the helix initiation motif of K13 are the cause of WSN in these families. These cases confirm mutations in the mucosal specific keratins as a significant cause of the disorder.