Furthermore, recent studies have shown that truncation mutations in the TTN gene, the most common DCM causative mutations, can cause alcoholic cardiomyopathy (3), peripartum cardiomyopathy (4), and chemotherapy-related cardiomyopathy (5), suggesting that a second hit caused by environmental factors in addition to genetic factors induces DCM-like contractile dysfunction. Here, TTN is linked to familial dilated cardiomyopathy.