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Key Clinical Message Homozygous variants of Calcium Voltage‐Gated Channel Subunit Alpha1 S (CACNA1S) gene mutation were previously identified as causes of periodic paralysis and congenital early‐onset myopathy, while it could be manifested as a late‐onset congenital core myopathy. Abstract Calcium Voltage‐Gated Channel Subunit Alpha1 S (CACNA1S) gene mutation has been linked to various neuromuscular conditions in recent years. Congenital myopathy with core‐like features is one of the cardinal associations reported previously, causing severe respiratory insufficiency and death in neonates. Informed consent was received from the patients. Subsequently, peripheral blood leukocytes were utilized to extract genomic DNA. Moreover, exome enrichment was implemented through the Twist Human Core Exome Kit (Twist Bioscience) and exome sequenced using Illumina NovaSeq 6000 platform (Illumina, San Diego, CA, USA). Sanger sequencing using BIG Dye Terminators confirmed the presence of the final variant. Finally, the candidate variants were classified based on the American College of Medical Genetics and Genomics (ACMG) guidelines. In this report, we describe two siblings, who presented with childhood and late‐onset progressive muscle weakness, and had a homozygous variant in exon 2 of the CACNA1S gene defined as c.188C > A (p.Ala63Asp) (NM_000069.3). The SIFT, Polyphen2, CADD PHRED, and Mutation Taster analysis tools classified the variant as pathogenic/damaging. The muscle biopsy of the younger brother revealed intermyofibrillar network pattern disruption as cytoplasmic core‐like lesions. The muscle magnetic resonance imaging (MRI) reported grade IIa and IIb fatty changes. Finally, the electromyography (EMG) findings suggested a myopathic change pattern. This report illustrates the clinical variability in CACNA1S‐related myopathy by reviewing prior reports and adding newly found aspects, additionally expanding the gene defects associated with core myopathy.

Abstract Next-generation sequencing (NGS) has been proven to be one of the most powerful diagnostic tools for rare Mendelian disorders. Several studies on the clinical application of NGS in unselected cohorts of Middle Eastern patients have reported a high diagnostic yield of up to 48%, correlated with a high level of consanguinity in these populations. We evaluated the diagnostic utility of NGS-based testing across different clinical indications in 1436 patients from Iran, representing the first study of its kind in this highly consanguineous population. A total of 1075 exome sequencing and 361 targeted gene panel sequencing were performed over 8 years at a single clinical genetics laboratory, with the majority of cases tested as proband-only (91.6%). The overall diagnostic rate was 46.7%, ranging from 24% in patients with an abnormality of prenatal development to over 67% in patients with an abnormality of the skin. We identified 660 pathogenic or likely pathogenic variants, including 241 novel variants, associated with over 342 known genetic conditions. The highly consanguineous nature of this cohort led to the diagnosis of autosomal recessive disorders in the majority of patients (79.1%) and allowed us to determine the shared carrier status of couples for suspected recessive phenotypes in their deceased child(ren) when direct testing was not possible. We also highlight the observations of recessive inheritance of genes previously associated only with dominant disorders and provide an expanded genotype–phenotype spectrum for multiple less-characterized genes. We present the largest mutational spectrum of known Mendelian disease, including possible founder variants, throughout the Iranian population, which can serve as a unique resource for clinical genomic studies locally and beyond.

Background: Diagnosis of hereditary hearing loss (HHL) as a heterogeneous disorder is very important espe-cially in countries with high rates of consanguinity where the autosomal recessive pattern of inheritance is preva-lent. Techniques such as next-generation sequencing, a comprehensive genetic test using targeted genomic en-richment and massively parallel sequencing (TGE + MPS), have made the diagnosis more cost-effective. The aim of this study was to determine HHL variants with comprehensive genetic testing in our country. Methods: Fifty GJB2 negative individuals with HHL were referred to the Kariminejad-Najmabadi Pathology and Genetics Center, Tehran, one of the reference diagnostic genetic laboratories in Iran, during a 3-year period between 2014 and 2017. They were screened with the OtoSCOPE test, the targeted genomic enrichment and massively parallel sequencing (TGE + MPS) platform after a detailed history had been taken along with clinical evaluation. Results: Among 32 out of 50 GJB2 negative patients (64%), 34 known pathogenic and novel variants were de-tected of which 16 (47%) were novel, identified in 10 genes of which the most prevalent were CDH23, MYO7A and MYO15A. Conclusion: These results provide a foundation from which to make appropriate recommendations for the use of comprehensive genetic testing in the evaluation of Iranian patients with hereditary hearing loss.