For example, patients with identical cardiomyopathy-causing mutations, such as mutations in RBM20, TNNI3 or BAG3, can manifest highly variable disease onset and severity (Arad et al., 2002; Hwang et al., 2017; Norton et al., 2011; Pantou et al., 2018). This evidence concerns the gene BAG3 and cardiomyopathy.