However, the high frequency of variants in TTN (Akinrinade, Koskenvuo, & Alastalo, 2015), incomplete penetrance (Golbus et al., 2012; McNally, 2012), and limited understanding of the spectrum of disease, particularly neuromuscular disease, has led to uncertainties in determining the clinical significance of TTN variants, and many identified in clinical practice are dismissed as incidental. This evidence concerns the gene TTN and neuromuscular disease.