In this study, the pathogenicity of the MYH7 c.2770G > A (p.Glu924Lys) mutation was confirmed for the first time in a Chinese polyphenotypic cardiomyopathy family line, thereby revealing its clinical features leading to significant phenotypic heterogeneity and a propensity for rapid progression. The gene discussed is MYH7; the disease is cardiomyopathy.