The genetic basis of arrhythmogenic right ventricular cardiomyopathy (ARVC) is complex. Mutations in genes encoding components of the cardiac desmosomes have been implicated as being causally related to ARVC. Next-generation sequencing allows parallel sequencing and duplication/deletion analysis of many genes simultaneously, which is appropriate for screening of mutations in disorders with heterogeneous genetic backgrounds. We designed and validated a next-generation sequencing test panel for ARVC using HaloPlex. We used SureDesign to prepare a HaloPlex enrichment system for sequencing of DES, DSC2, DSG2, DSP, JUP, PKP2, RYR2, TGFB3, TMEM43, and TTN from patients with ARVC using a MiSeq instrument. Performance characteristics were determined by comparison with Sanger, as the gold standard, and TruSeq Custom Amplicon sequencing of DSC2, DSG2, DSP, JUP, and PKP2. All the samples were successfully sequenced after HaloPlex capture, with >99% of targeted nucleotides covered by >20×. The sequences were of high quality, although one problematic area due to a presumptive context-specific sequencing error-causing motif located in exon 1 of the DSP gene was detected. The mutations found by Sanger sequencing were also found using the HaloPlex technique. Depending on the bioinformatics pipeline, sensitivity varied from 99.3% to 100%, and specificity varied from 99.9% to 100%. Three variant positions found by Sanger and HaloPlex sequencing were missed by TruSeq Custom Amplicon owing to loss of coverage.

Background Pathogenic variants in the SMAD3 gene affecting the TGF‐β/SMAD3 signaling pathway with aortic vessel involvement cause Loeys‐Dietz syndrome 3, also known as aneurysms–osteoarthritis syndrome. Methods Description of clinical history of a family in Sweden using clinical data, DNA sequencing, bioinformatics, and pedigree analysis. Results We report a novel SMAD3 variant, initially classified as a genetic variant of uncertain clinical significance (VUS), and later found to be co‐segregating with aortic dissection in the family. The index patient presented with a dissecting aneurysm of the aorta including the ascending, descending, and abdominal parts. Genotype analysis revealed a heterozygous missense SMAD3 variant: NM_005902.3(SMAD3): c.11576G > C (p.Arg386Thr). The same variant was also identified in a 30 years old formalin‐fixed paraffin‐embedded block of tissue from a second cousin, who died at 26 years of age from a dissecting aneurysm of the aorta. Conclusion A “variant of uncertain significance” according to the ACMG guidelines has always a scope for reappraisal. Genetic counselling to relatives, and the offering of surveillance service is important to families with aortic aneurysm disease. The report also highlight the potential use of FFPE analysis from deceased relatives to help in the interpretation of variants.

No abstract

This new plakophilin mutation demonstrates variable penetrance and phenotypic expression in ARVC, and highlights the need of genetic testing and thorough phenotype examination in ARVC pedigrees.

The cover image is based on the Clinical Report Novel SMAD3 p.Arg386Thr genetic variant co‐segregating with thoracic aortic aneurysm and dissection by Karolina Engström et al., https://doi.org/10.1002/mgg3.1089.