MYBPC3 and hypertrophic cardiomyopathy: In the BIO FOr CARe (Identification of BIOmarkers of hypertrophic cardiomyopathy development and progression in Dutch MYBPC3 FOunder variant CARriers) study we aim to investigate predictive factors and effect modifiers for penetrance and progression of HCM in the genetically homogeneous group of Dutch carriers of truncating MYBPC3 variants.