They form the most frequent indication for cardiac transplantation. Duchenne and Becker muscular dystrophies often produce some very similar cardiac symptoms. Dilated cardiomyopathy is a biochemical abnormality of cardiac muscle in which the heart chambers become grossly enlarged, with a greatly reduced contractility. It is a relatively common disease with an incidence of about 37 per 100,000. The disease is heterogenous and no specific genetic defect has yet been clearly identified.
Hypertrophic cardiomyopathies are a group of familial disorders.
There is a first class American website on all types of cardiomyopathy maintained by the National Heart Lung and Blood Institute that is well worth visiting. It includes a useful glossary for beginners. The post mortem specimen below illustrates some of the pathological changes seen in dilated cardiomyopathy. The left ventricle is grossly enlarged and the muscular walls are abnormally thin, in relation to the size of the ventricle. This is an image map, and the major features can be identified by pointing at them with the mouse.