While HCM has been attributed to monogenic perturbations in sarcomeric genes, like MYBPC3 and MYH7, there is often dramatic phenotypic variability, even within a single family, with some family members having other cardiomyopathy subtypes, including DCM and ARVC, or hybrid phenotypes. This evidence concerns the gene MYBPC3 and arrhythmogenic right ventricular cardiomyopathy.