Recently, mutations of keratin 1 gene (KRT1) and keratin 10 gene (KRT10) have been reported in various patients with bullous congenital ichthyosiform erythroderma (BCIE). The substitution of arginine (R) to histidine (H) at amino acid residue 156 (R156H) of coiled 1A region is one of the most frequent mutations of KRT10. In this study, we searched for a mutation in KRT1 and KRT10 in a Japanese family with BCIE and detected mutation R156H in KRT10. Our search led to the detection of R156H. This mutation was not detected in 50 normal individuals. These results confirmed that codon 156 is a frequently mutated site, and that R156H in KRT10 is likely also to be a mutation hotspot in Japanese patients with BCIE.