TTN and familial dilated cardiomyopathy: TTN mutations, whether recessive or dominant, are also emerging as major causes of dilated cardiomyopathy [3, 18, 43, 59, 60] and have been implicated in hypertrophic cardiomyopathy (HCM) [35], however no families with co-segregation of TTN missense variants with HCM or DCM have been identified to date [1, 56].