Genetical, clinical, and functional analysis of a large international cohort of patients with autosomal recessive congenital ichthyosis due to mutations in NIPAL4.

Autosomal recessive congenital ichthyosis (ARCI) belongs to a heterogeneous group of disorders of keratinization. To date, 10 genes have been identified to be causative for ARCI. NIPAL4 (Nipa-Like Domain-Containing 4) is the second most commonly mutated gene in ARCI. In this study, we present a large cohort of 101 families affected with ARCI carrying mutations in NIPAL4. We identified 16 novel mutations and increase the total number of pathogenic mutations in NIPAL4 to 34. Ultrastructural analysis of biopsies from six patients showed morphological abnormalities consistent with an ARCI EM type III. One patient with a homozygous splice site mutation, which leads to a loss of NIPAL4 mRNA, showed additional ultrastructural aberrations together with a more severe clinical phenotype. Our study gives insights into the frequency of mutations, a potential hot spot for mutations, and genotype-phenotype correlations.

The Position of Targeted Next-generation Sequencing in Epidermolysis Bullosa Diagnosis.

The precise classification of epidermolysis bullosa (EB) into 4 main types and more than 30 subtypes is based on the level of skin cleavage, as well as clinical and molecular features, and is crucial for early prognostication, case management, genetic counselling and prenatal or pre-implantation diagnosis. We report here the molecular pathology of 40 consecutive cases of suspected EB, which were investigated by immunofluorescence mapping (IFM) and/or by a targeted next-generation sequencing (NGS) multi-gene panel. IFM correctly established the EB subtype in 76% of cases, while the molecular pathology was completely elucidated in 90% of cases by the targeted NGS multi-gene panel. Thirteen previously unreported mutations in EB genes were identified. In cases with unclear clinical and IFM findings, mutations were found by NGS in previously unexpected genes. IFM was useful in delivering fast results in newborns, and in indicating the consequences of the variants of uncertain significance on protein level. This study underscores the efficacy of the strategy of combining targeted NGS with IFM in resolving unusual EB phenotypes. It also suggests that, despite technological advances, careful clinical evaluation and deep phenotyping remains a crucial factor that dictates successful diagnosis of EB.