Molecular characterization of ichthyoses. New aspects of terminology and classification

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.