The severity of the phenotype and copresentation of cardiac and skeletal myopathy could well be due to the presence of 2 mutant copies of MYH7. Considering the high degree of conservation, however, and the indisputable role of electrostatic interactions in maintaining tail–tail contacts in the thick filaments, the severe Glu to Lys charge reversal may likely be the underlying cause of myocardial involvement. This evidence concerns the gene MYH7 and skeletal muscle disorder.