Uncovering the gene variants in a global cohort of patients with unexplained increased left ventricular wall thickness using next-generation sequencing

Genetic analysis using massive parallel sequencing is crucial for the accurate and early diagnosis of hereditary hypertrophic cardiomyopathies and their phenocopies, especially transthyretin cardiac amyloidosis (ATTR-CA) and Fabry disease (FD). This study extends the cardio next-generation sequencing (NGS) pilot study by investigating the detection rate of gene variants causing increased left ventricular wall thickness (LVWT) using an expanded 19-gene NGS panel in a larger global cohort. This study included 2068 patients with unexplained increased LVWT enrolled at cardiological clinics across 22 countries/regions between 2020 and 2022. The NGS panel comprised 19 genes associated with hypertrophic cardiomyopathy (HCM) and its phenocopies. Sequencing was performed using the Illumina NextSeq 500 and NovaSeq 6000 systems, with variant interpretation performed according to the American College of Medical Genetics and Genomics guidelines. Novel variants were analyzed using the Human Gene Mutation Database (HGMD®), Franklin, and VarSome. Among the 2068 patients, 453 patients were positive for pathogenic/likely pathogenic variants (21.9%). The diagnostic yield for HCM was 18.4%, while that of HCM phenocopies was 3.5%, including ATTR-CA (1.5%), and FD (0.9%). In patients with a positive test (HCM or HCM phenocopies), the most prevalent HCM-related variants were MYBPC3 and MYH7 (36.4% and 34.4% of all positive samples, respectively), whereas TTR (7.1%) and GLA (4.0%) were the most common phenocopy variants. Other classical phenocopies, Noonan syndrome, Danon disease, and PRKAG2, comprised another 2.0%, 0.9%, and 0.7% of the cohort, respectively. The mean ages for patients with HCM sarcomeric gene variants, HCM phenocopy variants, FD, and ATTR-CA were 45.1 ± 17.6, 50.9 ± 23.7, 51.1 ± 19.4, and 64.6 ± 19.0 years, respectively. This study demonstrates the need to include GLA and TTR in NGS panels for patients with increased unexplained LVWT. NGS effectively identifies phenocopies often missed by imaging. Using a large, diverse cohort, this study reveals the prevalence of FD and ATTR-CA in patients with unexplained increased LVWT, reinforcing the importance of NGS for early diagnosis and targeted therapy.