Analysis of the KRT9 Gene in a Mexican Family with Epidermolytic Palmoplantar Keratoderma

Abstract Epidermolytic palmoplantar keratoderma ( EPPK ), an autosomal‐dominant genodermatosis, is the most frequently occurring hereditary palmoplantar keratoderma. EPPK is characterized by hyperkeratosis of the palms and soles. Approximately 90% of patients present with mutations in the KRT 9 gene, which encodes for keratin 9. Many of these mutations are located within the highly conserved coil 1A region of the alpha‐helical rod domain of keratin 9, an important domain for keratin heterodimerization. The objective was to assess the clinical and molecular characteristics of a M exican family with EPPK . The clinical characteristics of members of this family were analyzed. The KRT 9 gene of affected members was polymerase chain reaction amplified from genomic DNA and sequenced. All affected members of the family had hyperkeratosis of the palms and soles with knuckle pads. The R 163 W mutation in the KRT 9 gene was present in all affected individuals who were tested. Although R 163 W is the most frequent KRT 9 mutation in patients with EPPK , only two families have been reported with knuckle pads associated with this mutation. Our findings indicate that knuckle pads can be associated with EPPK and the R 163 W mutation in a family with a genetic background different from that described here.