Exhaustive structure-function aspects of Nav1.4 channels, Nav1.4 GoF mutations and related channelopathies are well discussed in recent reviews and are not the scope here (Cannon, 2018; Catterall et al., 2020; Maggi et al., 2021; Mantegazza et al., 2021; Meisler et al., 2021). This evidence concerns the gene SCN4A and channelopathy.