A novel H1 domain mutation in the keratin 2 gene in a Japanese family with ichthyosis bullosa of Siemens

Abstract

Conflicts of interest: none declared. Ichthyosis bullosa of Siemens (IBS) is a rare autosomal dominant skin disorder characterized by blister formation in the upper suprabasal layers of the epidermis. Clinical features of the disease, which include blistering after mechanical trauma, lichenified hyperkeratosis over the flexural areas of the limbs, and superficial peeling of the skin, are similar to those of epidermolytic hyperkeratosis/bullous congenital ichthyosiform erythroderma (EHK/BCIE). This clinical resemblance makes diagnosis difficult. Recent molecular studies have identified mutations in the keratin 2 (K2) gene (KRT2; this new designation is used throughout this report according to the current nomenclature for mammalian keratins1) in patients with IBS, in contrast to the keratin 1 or 10 mutations that have been detected in patients with EHK/BCIE, enabling us to differentiate between IBS and EHK/BCIE.2 Thus far, 29 missense mutations that result in amino acid substitutions in K2 have been identified in patients with IBS; all such mutations reside in the helix initiation or termination motifs of K2. Here, we describe a novel mutation in the H1 region of K2 in a Japanese family with IBS.