Several known mutations of SCN4A associated with PMC, including p.Q270K (located in DI/S5–6 segments), p.N440K (in DI/S6), p.G1306E, p.T1313A, N1366S, and p.R1448P (all in DII-IV linker), are also known to result in the impairment of inactivation process and a slowing of the macroscopic inactivation kinetics of the channel [10,11,12,13,14,15,16]. This evidence concerns the gene SCN4A and paramyotonia congenita of Von Eulenburg.