RBM20 and familial dilated cardiomyopathy: Conversely, all reported human carriers of pathogenic genetic variants in RBM20 are heterozygous and most develop severe disease, as evidenced by the requirement for heart transplantation at earlier age in RBM20 variant carriers compared to that in carriers of pathogenic genetic variants in other DCM-associated genes (Kayvanpour et al. 2017).