Restrictive cardiomyopathy is a heart muscle disorder characterized by increased myocardial stiffness that results in an abnormally steep rise in intraventricular pressure with small increases in volume in the presence of normal or decreased diastolic left ventricular volumes and normal ventricular wall thickness. The disease may be caused by mutations in a number of genes or myocardial infiltration. Arrhythmogenic right ventricular cardiomyopathy is an inherited cardiac muscle disease associated with sudden cardiac death, ventricular arrhythmias, and cardiac failure. It is most frequently caused by mutations in desmosomal protein genes that lead to fibrofatty replacement of cardiomyocytes, right ventricular dilatation, and aneurysm formation.