Mild phenotype of epidermolytic hyperkeratosis mimicking ichthyosis bullosa of Siemens is related to specific mutation in 2B domain of KRT1

De Novo Mutation in KRT1 Leads to Epidermolytic Palmoplantar Keratoderma: from Chinese Traditional Treatment to Prenatal Diagnosis Using Whole-Exome Sequencing-Plus

Congenital skin disorders are a class of complex genetic diseases that are difficult to diagnose and treat. We developed trio whole-exome sequencing-plus (WES-plus) for detecting de novo mutations and evaluated the use of traditional Chinese medicine (TCM) for treating congenital skin disorders. In this study, we successively performed panel-based next-generation sequencing (NGS) and Trio WES-plus in a child with frequent large blisters. Panel-based NGS revealed no pathogenic mutations. Trio WES-plus for resequencing based on cutaneous keratosis of the palms and feet detected a missense mutation (c.1436T>A, p.Ile479Asn) in the coding region of KRT1 in the child but not in his parents. Following prenatal diagnosis, a healthy second baby without the mutation was born. The disease symptoms of epidermolytic palmoplantar keratoderma (EPPK) application were improved by TCM and Western medicine. Our study revealed the pathogenicity of a de novo mutation in human KRT1, which expands the mutation spectrum of EPPK. Trio WES-plus is useful for diagnosing genetic diseases and providing genetic guidance from prenatal diagnosis to treatment.

A novel KRT1 c.1433A>G p.(Glu478Gly) mutation in a newborn with epidermolytic ichthyosis

Epidermolytic Ichthyosis is a rare genodermatosis related to point mutations affecting the genes encoding for keratin 1 or keratin 10. We report a case of Epidermolytic Ichthyosis in a newborn with a novel mutation (c.1433A>G) of KRT1 gene.

Mutations Affecting Keratin 10 Surface-Exposed Residues Highlight the Structural Basis of Phenotypic Variation in Epidermolytic Ichthyosis

Epidermolytic ichthyosis (EI) due to KRT10 mutations is a rare, typically autosomal dominant, disorder characterized by generalized erythema and cutaneous blistering at birth followed by hyperkeratosis and less frequent blistering later in life. We identified two KRT10 mutations p.Q434del and p.R441P in subjects presenting with a mild EI phenotype. Both occur within the mutational "hot spot" of the keratin 10 (K10) 2B rod domain, adjacent to severe EI-associated mutations. p.Q434del and p.R441P formed collapsed K10 fibers rather than aggregates characteristic of severe EI KRT10 mutations such as p.R156C. Upon differentiation, keratinocytes from p.Q434del showed significantly lower apoptosis (P-value<0.01) compared with p.R156C as assessed by the TUNEL assay. Conversely, the mitotic index of the p.Q434del epidermis was significantly higher compared with that of p.R156C (P-value<0.01) as estimated by the Ki67 assay. Structural basis of EI phenotype variation was investigated by homology-based modeling of wild-type and mutant K1-K10 dimers. Both mild EI mutations were found to affect the surface-exposed residues of the K10 alpha helix coiled-coil and caused localized disorganization of the K1-K10 heterodimer. In contrast, adjacent severe EI mutations disrupt key intermolecular dimer interactions. Our findings provide structural insights into phenotypic variation in EI due to KRT10 mutations.