TTN and familial dilated cardiomyopathy: The putative DCM genes are involved in various cellular functions within cardiomyocytes including contractile apparatus (sarcomeres), calcium cycling, nuclear membranes, heat shock chaperones, mitochondria, and cell adhesion.8 Pathogenic variants in gene titin (TTN) are the most common genetic cause of adult-onset DCM, found in 15% to 20% of affected individuals, but rarely identified in childhood-onset DCM.9,10 TTN serves as a scaffold to support formation of the contractile apparatus and a molecular spring that influences contractility and relaxation.