A a genetic form of heart disease that occurs when heart (cardiac) muscle becomes thin and weakened in at least one chamber of the heart, causing the open area of the chamber to become enlarged (dilated). As a result, the heart is unable to pump blood as efficiently as usual. To compensate, the heart attempts to increase the amount of blood being pumped through the heart, leading to further thinning and weakening of the cardiac muscle. Over time, this condition results in heart failure. The disease is Monarch Disease Ontology entry MONDO_0016333 (familial dilated cardiomyopathy). Also known as: hereditary dilated cardiomyopathy.