R162W mutation of keratin 9 in a family with autosomal dominant palmoplantar keratoderma with unique histologic features.

Recurrent R162W mutation ofkeratin 9 has been reported in multiple families with epidermolytic hyperkeratosis (EHK)-type hereditary palmoplantar keratoderma (PPK). Recently, we have observed a family whose members showed autosomal-dominant PPK with unique histologic features such as rounded, dissociated, and slightly eosinophilic keratinocytes at the middle spinous and granular layers of epidermis, but without the distinct EHK phenotype. To investigate the genotype-phenotype correlation in this family, we searched for a mutation of keratin 9 and found R162W substitution in the coiled 1A region. This mutation was not detected in 50 control individuals. These results may further our understanding of the pathogenesis of EHK.