Different mutations usually account for different ion channel characteristics and phenotypes, although some of the mutations can cause several phenotypes.2 The c.3466G>A p.A1156T mutation has been reported with most of the SCN4A manifestations: PMC, HyperPP, and pure myotonia.8,13 The articles describing these patients did not report myalgia as part of the clinical manifestation. Here, SCN4A is linked to hyperkalemic periodic paralysis.