Redefining the Genetic Architecture of Hypertrophic Cardiomyopathy: Role of Intermediate-Effect Variants

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is a genetically heterogeneous disorder linked primarily to rare variants in sarcomeric genes, although recently certain nonsarcomeric genes have emerged as important contributors. Nonmendelian genetic variants with reproducible moderate-effect sizes and low penetrance, intermediate-effect variants (IEVs), can play a crucial role in modulating disease expression. Understanding the clinical impact of IEVs is crucial to unravel the complex genetic architecture of HCM. METHODS: ). Enrichment of intermediate frequency missense variants was evaluated in 10 981 patients with HCM, 4030 internal controls of European-ancestry, and 590 000 external controls from gnomAD non-Finnish Europeans. The population-attributable fraction was calculated to assess contribution of IEVs to HCM. Age-related disease penetrance, phenotypic severity (left ventricular maximum wall thickness), and major adverse cardiac events were analyzed in 11 991 HCM cases of the whole cohort according to 5 genetic groups: genotype negative, isolated IEV, monogenic, monogenic+IEV, and double monogenic. RESULTS: <0.0001). CONCLUSIONS: IEVs are present in 6.1% of HCM cases and account for 4.8% of HCM genetic burden. IEVs also influence disease severity and outcomes, particularly when combined with monogenic disease-causing variants. Evaluation of IEVs should be considered when HCM genetic testing is performed.