Normokalemic periodic paralysis with involuntary movements and generalized epilepsy associated with two novel mutations in SCN4A gene

Mutations of skeletal muscle sodium channel a subunit (SCN4A) gene are associated with a group of allelic diseases, including periodic paralysis, paramyotonia congenital, sodium channel myotonia, and congenital myasthenic syndrome. Periodic paralysis is characterized by episodic attacks of flaccid weakness with the fluctuation of serum potassium, which are usually limited to skeletal muscles owing to tissue specific expression of channel isoforms. However, periodic paralysis is occasionally concomitant with cardiac arrhythmia, essential tremor, and epilepsy. Here we described a case of normokalemic periodic paralysis with involuntary movements and generalized epilepsy associated with two novel heterozygous missense mutations in SCN4A gene.