Misregulation of SCN5A splicing was specific to DM, as we did not observe inclusion of exon 6A in heart samples from individual affected with Duchenne muscular dystrophy (DMD), amyotrophic lateral sclerosis (ALS) or dilated cardiomyopathy (DCM) (Fig. 3d). Here, SCN5A is linked to familial dilated cardiomyopathy.