TNNI3 and cardiomyopathy, familial restrictive, 1: Since the first report of a familial form caused by a cardiac troponin I (TNNI3) variant [4], primary RCM was believed to be a sarcomeric disease and was labeled together with HCM as a sarcomeric cardiomyopathy (“sarcomyopathies”) according to a genomic/postgenomic classification [37,38,39,40].