It is suggested that RBM20 variants cause a particularly malignant form of DCM, characterized by fatal ventricular arrhythmia and rapidly progressive left ventricular systolic dysfunction (LVSD).6,7 If this is correct, diagnosis of pathogenic RBM20 variants has major implications for disease management and the counseling of families. This evidence concerns the gene RBM20 and familial dilated cardiomyopathy.