Objective: To explore the clinical and genetic characteristics of eight children with Primary hypertrophic cardiomyopathy (HCM).
Methods: Eight children with HCM admitted to the Department of Cardiology of Henan Children's Hospital from January 2018 to December 2021 were selected as the study subjects. Clinical data of the children were collected. Whole exome sequencing was carried out on two children, and trio whole exome sequencing was carried out on the remainder 6 children. Sanger sequencing was used to verify the candidate variants in the children and their parents, and the pathogenicity of the variants was evaluated based on the guidelines from the American College of Medical Genetics and Genomics (ACMG).
Results: The patients had included 5 males and 3 females, with their ages ranging from 5 to 13 years old. The average age of diagnosis was (7.87 ± 4.8) years old, and the cardiac phenotype showed non-obstructive HCM in all of the patients. WES has identified variants of the MYH7 gene in 4 children, including c.2155C>T (p.Arg719Trp), c.1208G>A (p.Arg403Gln), c.1358G>A (p.Arg453His), and c.1498G>A (p.Glu500Lys). Based on the guidelines from the ACMG, the first 3 variants were classified as pathogenic, while c.1498G>A (p.Glu500Lys) was classified as likely pathogenic (PM1+PM2_Supporting+PM6+PP3), which was also unreported previously. The remaining four children had all harbored maternal variants, including MYL2: c.173G>A (p.Arg58Gln; classified as pathogenic), TPM1: c.574G>A (p.Glu192Lys) and ACTC1: c.301G>A (p.Glu101Lys)(both were classified as likely pathogenic), and MYBPC3: c.146T>G (p.Ile49Ser; classified as variant of uncertain significance). Seven children were treated with 0.5 ~ 3 mg/(kg·d) propranolol, and their symptoms had improved significantly. They were followed up until September 30, 2022 without further cardiac event.
Conclusion: Genetic testing can clarify the molecular basis for unexplained cardiomyopathy and provide a basis for clinical diagnosis and genetic counseling. Discovery of the c.1498G>A (p.Glu500Lys) variant has also expanded the spectrum of MYH7 gene mutations underlying HCM.