Abstract 11792: Low Penetrance Sarcomere Variants Indicate an Additive Genetic Risk Model in Hypertrophic Cardiomyopathy

Abstract

Introduction: Genetic hypertrophic cardiomyopathy (HCM) is an autosomal dominant inherited condition primarily due to pathogenic variants in sarcomere genes, often with marked clinical variability. We hypothesized that this variability may, in part, be due to additive effects from low penetrance sarcomere variants that would otherwise be dismissed due to high population prevalence. Methods: Low-penetrance HCM-associated sarcomere gene variants were identified by meeting a threshold for enrichment in HCM (ascertained from the Sarcomeric Human Cardiomyopathy Registry, SHaRe) versus the general population (ascertained from the Genome Aggregation Database, gnomAD), defined by an odds ratio (OR) >5, and a population prevalence greater than the most common autosomal dominant pathogenic HCM variant, MYBPC3 R502W (4x10 -5 ). Clinical variables and time-event analyses were performed from SHaRe . Results: A total of 507 unique sarcomere gene variants were present in 6384 individuals with genetic testing. Ten putative low-penetrance variants were identified in the genes MYBPC3 (N=2), TNNT2 (N=1), TNNI3 (N=2), and MYH7 (N=5) with a combined OR of 12.7 (range 5.8 - 28.4). These variants had a population prevalence of 4.02x10 -5 to 3.5x10 -4 . Family members of low-penetrance variant carriers were less likely to have HCM (35/171, 20%) than those of MYBPC3 R502W carriers (44/113, 39%, p<0.005). Age of diagnosis was older in patients with isolated low-penetrance variants than those with pathogenic variants (42 ± 19 vs 37 ± 18, p=0.005). Composite adverse events were less likely in patients with isolated low-penetrance variants than typical pathogenic sarcomere variants, but the risk was additive with both present (see Figure). Conclusions: A subset of low-penetrance sarcomere gene variants are tolerated in the general population at higher than expected proportions for HCM and may exert an additive pathogenic effect. These findings support an oligogenic risk model of HCM.