This study aims to elucidate the pathogenicity of the TPM1 mutation (NM_001018005.2:c.541G>A, p. Glu181Lys) in restrictive cardiomyopathy (RCM), establish its ACMG pathogenicity classification, and report for the first time its association with sporadic RCM and underlying molecular mechanisms. The gene discussed is TPM1; the disease is restrictive cardiomyopathy.