Abstract
Methods of molecular cardiology have extended our knowledge of cardiomyopathies. In hypertrophic cardiomyopathy the existence of at least nine beta-myosin heavy chain gene mutations on the arm of the 14th chromosome were detected.
The latter cause substitution of amino acids in the molecule of this protein with subsequent slowing of the actin shift against myosin during muscle contractions. The presence of beta-myosin heavy chain gene mutation is strictly specific for hypertrophic cardiomyopathy, the mutations cause not only familial cases of the disease but also its sporadic incidence.
There exists carriership of mutations, carriers can be quite healthy from the clinical aspect. Individual mutations differ by their penetrance and a different risk of sudden cardiac death. 100% penetrance and a high risk of sudden cardiac death are caused in particular by the mutation with substitution of glycine by arginine in position 403.
In addition to possible point mutations there are also mutations with deletion of a portion of this gene and also mutations on chromosomes 1, 11 and 15; so far, however, genes with these mutations were not identified. In dilated cardiomyopathy gene mutations are the cause of familial diseases which account for cca 20% of all these diseases.
Mutations can affect also the dystrophin gene on chromosome X, and genes of the mitochondrial genome which code in particular the primary structure of polypeptides participating in oxidative phosphorylation. Mutations as the cause of cardiomyopathies will probably call for a changed definition of these diseases.