Keratin 9 gene mutational heterogeneity in patients with epidermolytic palmoplantar keratoderma

Mutations in the human keratin 9 gene have recently been shown to be involved in the etiology of palmoplantar keratoderma (PPK). We have investigated eleven unrelated German kindreds with the epidermolytic variant of PPK (EPPK) for mutations in the keratin 9 gene. We have identified two novel mutations, M156V and Q171P, both in the coil 1A segment of keratin 9. Mutation M156V was detected in two unrelated patients with EPPK, and mutation Q171P was shown to cosegregate with the disease in a large four-generation family. These findings confirm the functional importance of coil 1A integrity for heterodimerisation in keratins and for intermediate filament assembly. Our results provide further evidence for mutational heterogeneity in EPPK, and for the involvement of keratins in diseases of hyperkeratinisation and epidermolysis.     

Molekulare Charakterisierung der Ichthyosen

Ichthyoses comprise an etiologically heterogeneous group of Mendelian disorders of cornification (MEDOC) that affect the entire integument and are characterized by hyperkeratosis and/or visible scaling. In recent years basic research has elucidated the genetic basis of almost all ichthyosis forms and enormously improved diagnostic facilities. The Network for Ichthyoses and Related Keratinization Disorders (NIRK; www.netzwerk-ichthyose.de) and the patient support organization Selbsthilfe Ichthyose e. V. (www.ichthyose.de) provide helpful contact points for physicians and patients in Germany. The first worldwide Ichthyosis Consensus Classification was approved in August 2009. Its nosology is based on clinical presentation but also reflects pathogenic aspects. The major criterion is the distinction between syndromic and non-syndromic forms. Controversial disease names have been re-defined: Ichthyoses due to keratin mutations are referred to under the new umbrella term keratinopathic ichthyosis (KPI), which comprises epidermolytic ichthyosis (mutation in keratin 1 or 10) and superficial epidermolytic ichthyosis (keratin 2). The term autosomal recessive congenital ichthyosis (ARCI) represents the umbrella for harlequin ichthyosis and for the group of lamellar ichthyosis and congenital ichthyosiform erythroderma. The international classification should serve as a reference for future research into these diseases, including further genotype-phenotype correlation studies.