True regarding cardiomyopathy

Most cardiac muscle diseases are secondary to some other condition, e.g., coronary atherosclerosis, hypeension, or valvular hea disease. However, there are also cardiac diseases attributable to intrinsic myocardial dysfunction. Such diseases are termed cardiomyopathies (literally, "hea muscle diseases"); these can be primary--that is, principally confined to the myocardium--or secondary presenting as the cardiac manifestation of a systemic disorder. Cardiomyopathies are thus a diverse group that includes inflammatory disorders (e.g., myocarditis), immunologic diseases (e.g., sarcoidosis), systemic metabolic disorders (e.g., hemochromatosis), muscular dystrophies, and genetic disorders of myocardial fibers. In many cases, the cardiomyopathy is of unknown etiology and thus is termed idiopathic; however, a number of previously "idiopathic" cardiomyopathies have been shown to be the consequence of specific genetic abnormalities in cardiac energy metabolism or in structural and contractile proteins. (Robbins Basic Pathology,9th edition,pg no.397)