In addition to myotonic diseases associated with SCN4A mutations, other diseases, that are beyond the scope of this review, also present mutations in this gene, such as: hyperkalemic periodic paralysis without myotonia (HyperPP), hypokalemic periodic paralysis (HyppoPP), normokalemic periodic paralysis (NormoPP), and congenital myasthenic syndrome (CMS) (20, 82). The gene discussed is SCN4A; the disease is hyperkalemic periodic paralysis.