Sporadic white sponge nevus caused by a mutation in the keratin 4 gene

Abstract Herein, we present a sporadic case of white sponge nevus (WSN) on the cheek mucosa in a 27-year-old Japanese man. A definite diagnosis of WSN was obtained using the typical clinical appearance and microscopic features of the lesions. Histopathological and cytological studies should be conducted to differentiate this condition from other oral premalignant white lesions. A molecular mutation analysis revealed a missense mutation in exon 1A of the keratin 4 gene, which is correlated with the development of WSN. Hence, genetic analysis must be performed to obtain an accurate diagnosis in sporadic cases. The temporary regression of the lesion after treatment with oral amoxicillin hydrate (AMPC) 750 mg/day indicates that antibiotics are effective in symptomatic cases.