The NDMs include myotonia congenita (MC) due to mutations in the skeletal muscle chloride channel gene CLCN1, paramyotonia congenita (PMC) and sodium channel myotonia (SCM), both of the latter are caused by mutations in the skeletal muscle sodium channel gene SCN4A encoding Nav1.4. This evidence concerns the gene CLCN1 and paramyotonia congenita of Von Eulenburg.