Genetic basis and outcome in a nationwide study of Finnish patients with hypertrophic cardiomyopathy

Aims Nationwide large‐scale genetic and outcome studies in cohorts with hypertrophic cardiomyopathy (HCM) have not been previously published. Methods and results We sequenced 59 cardiomyopathy‐associated genes in 382 unrelated Finnish patients with HCM and found 24 pathogenic or likely pathogenic mutations in six genes in 38.2% of patients. Most mutations were located in sarcomere genes (MYBPC3, MYH7, TPM1, and MYL2). Previously reported mutations by our study group (MYBPC3‐Gln1061Ter, MYH7‐Arg1053Gln, and TPM1‐Asp175Asn) and a fourth major mutation MYH7‐Val606Met accounted for 28.0% of cases. Mutations in GLA and PRKAG2 were found in three patients. Furthermore, we found 49 variants of unknown significance in 31 genes in 20.4% of cases. During a 6.7 ± 4.2 year follow‐up, annual all‐cause mortality in 482 index patients and their relatives with HCM was higher than that in the matched Finnish population (1.70 vs. 0.87%; P