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Truncating mutations in the TTN gene are the most common genetic cause of dilated cardiomyopathy in adults but their role in young patients is unknown. We studied 82 young dilated cardiomyopathy subjects and found that the prevalence of truncating TTN mutations in adolescents was similar to adults, but surprisingly few truncating TTN mutations were identified in affected children, including one confirmed de novo variant. In several cases, truncating TTN mutations in children with dilated cardiomyopathy had evidence of additional clinical or genetic risk factors. These findings have implications for genetic testing and suggest that single truncating TTN mutations are insufficient alone to cause pediatric-onset dilated cardiomyopathy.

Cardiomyopathy (CM) in children shares some features with cardiomyopathy in adults but also has many important unique features. Heretofore, genetic testing panels, testing strategies, and treatment recommendations have largely been based on studies in adult populations. In general, CMs in children are much more likely to be genetic and to have extracardiac manifestations that should be medically addressed. Therefore, genetic testing in children with CM is an essential part of their initial evaluation and the ongoing care of the child and family. CMs in children are more genetically heterogeneous, and many of the genes that are rare causes of CM in children are not currently included in testing panels, and future genetic testing is likely to increasingly utilize more comprehensive approaches such as whole exome/whole genome sequencing with focused analysis of all the genes that can cause CM in children.