Autosomal recessive congenital ichthyosis (ARCI), a phenotypically heterogeneous group of non‐syndromic Mendelian disorders of keratinization, is caused by mutations in as many as 13 distinct genes. We examined a cohort of 125 consanguineous families with ARCI for underlying genetic mutations. The patients’ DNA was analyzed with a gene‐targeted next generation sequencing panel comprising 38 ichthyosis associated genes. The interpretations of results of genomic data were assisted by genome‐wide homozygosity mapping and transcriptome sequencing. Sequence data analysis identified biallelic mutations in 106 families out of a total of 125 (85%), most of them (102, 96.2%) being homozygous, reflecting consanguinity in these families. Among the 85 distinct mutations in 10 different genes, 45 (53%) were previously unreported. Phenotype‐genotype correlations allowed assignment of specific genes in the majority of the families to a specific subtype of ARCI, lamellar ichthyosis (LI) versus congenital ichthyosiform erythroderma (CIE). Interestingly, mutations in several genes could give rise to an overlapping phenotype consistent with either LI or CIE. Also, this is the third report for SDR9C7 and SULT2B1, and fourth report for CERS3 mutations. Direct comparison of our results with previously published regional cohorts highlights the global mutation landscape of ARCI, however, population specific differences were noted.

Autosomal recessive congenital ichthyosis is a heterogeneous group of disorders associated with mutations in at least nine distinct genes. To ascertain the molecular basis of ichthyosis patients in Iran, a country of approximately 80 million people with a high prevalence of customary consanguineous marriages, we have developed a gene-targeted next generation sequencing array consisting of 38 genes reported in association with ichthyosis phenotypes. In a subset of nine extended consanguineous families, we found homozygous missense mutations in the PNPLA1 gene, six of them being distinct and, to our knowledge, previously unpublished. This gene encodes an enzyme with lipid hydrolase activity, important for development and maintenance of the barrier function of the epidermis. These six mutations, as well as four previously published mutations, reside exclusively within the patatin-like subdomain of PNPLA1 containing the catalytic site. The mutations clustered around the active center of the enzyme or resided at the surface of the protein possibly involved in the protein-protein interactions. Clinical features of the patients showed considerable intra- and interfamilial heterogeneity. Knowledge of the specific mutations allows identification of heterozygous carriers, assisting in genetic counseling, prenatal testing, and preimplantation genetic diagnosis in extended families at risk of recurrence of this disorder, the incidence of which is significantly increased in consanguineous marriages.

Dystrophic epidermolysis bullosa is a heritable skin disease manifesting with sub-lamina densa blistering, erosions, and chronic ulcers. COL7A1, encoding type VII collagen, has been identified as the candidate gene for dystrophic epidermolysis bullosa. In this study, we have identified COL7A1 mutations in a large multi-ethnic cohort of 152 extended Iranian families with high degree of consanguinity. The patients were diagnosed by clinical manifestations, histopathology, and immunoepitope mapping. Mutation detection consisted of a combination of single nucleotide polymorphism-based whole-genome homozygosity mapping, Sanger sequencing, and gene-targeted next-generation sequencing. A total of 104 distinct mutations in COL7A1 were identified in 149 of 152 families (98%), 56 (53%) of them being previously unreported. Ninety percent of these mutations were homozygous recessive, reflecting consanguinity in these families. Three recurrent mutations were identified in five or more families, and haplotype analysis suggested a founder effect in two of them. In conclusion, COL7A1 harbored mutations in the overwhelming majority of patients with dystrophic epidermolysis bullosa, and most of them in this Iranian cohort were consistent with autosomal recessive inheritance. The mutation profile attests to the impact of consanguinity in these families.