This cardiomyopathy associated with a glycogenin-1 mutation but without skeletal muscle weakness differs from the previously described cases who typically had a rather late onset skeletal myopathy without cardiomyopathy (Malfatti et al 2014; Colombo et al 2016; Fanin et al 2015; Luo et al 2015; Akman et al 2016). This evidence concerns the gene GYG1 and cardiomyopathy.