Dominant SCN4A gain-of-function mutations are a well-established cause of myotonia and periodicparalysis.
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Methods: Six unrelated Korean patients with periodicparalysis or nondystrophic myotonia associated with SCN4A mutations were included in the study.
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Hypokalaemic periodicparalysis is a rare genetic neuromuscular disease characterized by episodes of skeletal muscle paralysis associated with low serum potassium.
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We report a child with hypokalaemic periodicparalysis and CNS involvement, including seizures, but without mutations in the known periodicparalysis genes.
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There are at present two other distinct clinical muscle disorders associated with mutations in the sodium channel: hyperkalemic periodicparalysis and paramyotonia congenita.