title: Familial hyperkalemic periodic paralysis caused by a de novo mutation in the sodium channel gene SCN4A.
abstract: Familial hyperkalemic periodic paralysis (HYPP) is an autosomaldominant channelopathy characterized by transient and recurrent episodes of paralysis with concomitant hyperkalemia. Mutations in the skeletal muscle voltage-gated sodium channel gene SCN4A have been reported to be responsible for this disease. Here, we report the case of a 16-year-old girl with HYPP whose mutational analysis revealed a heterozygous c.2111C>T substitution in the SCN4A gene leading to a Thr704Met mutation in the protein sequence. The parents were clinically unaffected and did not have a mutation in the SCN4A gene. A de novo SCN4A mutation for familial HYPP has not previously been reported. The patient did not respond to acetazolamide, but showed a marked improvement in paralytic symptoms upon treatment with hydrochlorothiazide. The findings in this case indicate that a de novo mutation needs to be considered when an isolated family member is found to have a HYPP phenotype.
authors.affiliation: Department of Pediatrics, Konyang University College of Medicine, Daejeon, Korea.
authors.forename: Ji-Yeon
authors.initials: JY
authors.lastname: Han
authors.forename: June-Bum
authors.initials: JB
authors.lastname: Kim