Background White sponge nevus is a rare autosomal dominant disorder that affects the non‐keratinised stratified squamous epithelium. Mutations in the genes that encode mucosa‐specific keratin‐4 and keratin‐13 are strongly linked to the manifestation of white sponge nevus. This study involved mutational analysis of the genes encoding keratin‐4 and keratin‐13 in two Swedish families with white sponge nevus. Methods The diagnosis of white sponge nevus was based on disease history, clinical characteristics of the lesions and, in the majority of the cases, histopathological examination. Samples were collected from the affected buccal mucosa using buccal swabs. DNA was subsequently extracted and amplified using touchdown‐PCR. The keratin‐4 and keratin‐13 genes were sequenced, and a genetic analysis was performed. Results A novel heterozygous missense mutation was identified in exon 1A of the keratin‐4 gene in Family 2. In addition, previously reported heterozygous missense mutations were identified in the keratin‐4 (E449K, A72V, Q156R, R208H) and keratin‐13 (L115P) genes in both families. Conclusion We describe a novel heterozygous missense mutation in the keratin‐4 gene of a Swedish family with white sponge nevus. Our results support the notion that mutations in keratin‐4 and keratin‐13 are the underlying cause of white sponge nevus.