TTN and familial dilated cardiomyopathy: Truncating variants in titin (TTNtv) are the most frequent genetic finding in idiopathic DCM, being present in 15% to 25% of the cases,32 and are also frequent in peripartum cardiomyopathy (15%).33 However, penetrance seems to be low because TTNtv are also found in ≈1% of normal populations, and hence, the large majority of carriers do not manifest with disease.34 More recent work35 showed that DCM causing TTNtv are enriched in the sarcomeric A-band region, whereas TTNtv found in control cohorts tend to spare the A-band region and are in exons, with low usage in cardiac transcripts.