TTN and familial dilated cardiomyopathy: It is found in the sarcomere where it spans from the Z-disk to the M-band, and is critical for sarcomere assembly, contraction and relaxation in striated cardiac muscle.1 In populations largely composed of individuals genetically similar to the 1000 Genomes Project (1000G) European reference population (EUR), heterozygous TTN truncating variants (TTNtvs) that encode for shortened forms of the titin protein have been identified as a common genetic cause of dilated cardiomyopathy (DCM).