Familial paroxysmal kinesigenic dyskinesia with a novel missense variant (Arg2866Trp) in NBEA

Paroxysmal kinesigenic dyskinesia (PKD) is a movement disorder characterized by episodic involuntary movement attacks triggered by sudden movements, acceleration, or intention to move. We ascertained two Japanese familial cases with PKD. The proband is a 22-year-old woman who had noted sudden brief ( C [p.Gln2992His] in FAT2 and NM_015678: c.8596C > T [p.Arg2866Trp] in NBEA). Real time quantitative PCR analysis of Nbea mRNA levels in the developing rat brain revealed peak at postnatal day 28 and decline at postnatal day 56. This result might match the most common clinical course of PKD from the point of view of the most common age at remission. NBEA has been reported to be responsible for neurodevelopmental disease accompanied by epilepsy. We concluded the variant in NBEA most likely to be responsible for our familial cases of PKD.