Factors Affecting the Genetic Diagnostic Rate in Congenital Heart Disease

Background: Over 400 genes contribute to the development of congenital heart disease (CHD). Additionally,multisystemic manifestations accompanying syndromic CHD pose a higher risk of genetic diseases. This studyinvestigated the diagnostic yield of whole-exome sequencing (WES) in patients with sporadic syndromic CHDand the phenotypic factors affecting the genetic diagnostic rate. Methods: Sixty-four patients with sporadic syndromicCHD aged <18 years underwent WES between May 2018 and December 2020 in a single tertiary center,and the association between genetic testing data and extracardiac phenotypes was analyzed. Results: Extracardiacphenotypes were measured as 3.66 ± 3.05 (standard deviation, interquartile range: 2–5) items per patient. WESdetected diagnostic variants in 19 (29.7%) patients: seven (36.8%), seven (36.8%), and five (26.3%) with pathogenicvariants, likely pathogenic variants, and variants of unknown significance, respectively. Post-diagnosis surveillanceidentified the extracardiac phenotype in 54.5% (6/11) of patients. De novo variants accounted for 76.2%(15/19) of variants and autosomal dominant inheritance for 94.7% (18/19). Most diseases were ultra-rare. No significantdifferences were noted in cardiac and extracardiac phenotypes, single or combined (all P > 0.05), betweenthe groups with and without a diagnostic variant. However, patients with ≥3 extracardiac phenotypes had a significantlyhigher likelihood of having a diagnostic variant than those with ≤2 (38.3% vs. 5.9%, odds ratio = 9.93,95% confidence interval = 1.21–81.44, P = 0.013). Conclusions: The number of extracardiac phenotypes is importantin predicting the possibility of genetic diagnosis. Physicians will be able to select patients with a high probabilityof genetic diagnosis and provide appropriate genetic counseling based on the results of this study.

High Prevalence of Genetic Alterations in Infantile-Onset Cardiomyopathy

Background and Method:The genetic cause of infantile-onset cardiomyopathy is rarely investigated.Here,we conducted whole exome sequencing(WES)and mitochondrial DNA(mtDNA)sequencing in eight patients with infantile-onset cardiomyopathy to identify genetic variations.Result:Among these patients,two(25%)had dilated cardiomyopathy(DCMP),two(25%)had left ventricular non-compaction(LVNC),and four(50%)had hypertrophic cardiomyopathy(HCMP).Except four patients identified prenatally,the remaining patients presented at a median age of 85.5 days.WES identified genetic variants in a total of seven(87.5%)patients and mtDNA sequencing in the other case.TPM1 and MYH7 variants were identified in the two patients with DCMP;MYH11 and MYLK2 variants in the two patients with LVNC;HRAS,BRAF,and MYH7 variants in three patients with HCMP;and MT-ND1 variant in one patient with HCMP having high blood lactic acid levels.Among the eight variants,four were classified as pathogenic or likely-pathogenic according to the American College of Medical Genetics(ACMG)guidelines,and the remaining were identified as variants of unknown significance(VUSs).Three pathogenic mutations were de novo,whereas four(likely-pathogenic or VUSs)were inherited from a respective parent,excluding one variant where parental testing was unavailable,questioning whether these inherited variants are disease-causing.Three patients died before 3 months of age.Conclusion:Genomic studies,such as WES with additional mtDNA sequencing,can identify a genetic variant in high proportions of patients with infantile-onset cardiomyopathy.The clinical implication of the parentally inherited variant needs to be assessed in a larger patient and family cohort with a longitudinal follow-up.