Taking into account the absence of stable and long-lasting arterial hypertension, hypertrophy of the myocardium up to 14 mm with a decrease in its contractility, absence of left ventricle dilatation, low voltage of the QRS complexes in ECG and a stable and prominent increase in plasma CPK (from 700 to 3300 U/L), in combination with symptoms of peripheral myopathy, it is reasonable to make a diagnosis of long-lasting symptomless primary cardiomyopathy with a mixed phenotype within a frame of neuromuscular disease that serves as a basis for arrhythmia. The gene discussed is PIK3C2A; the disease is cardiac arrhythmia.