[Background]: The mutations in PRRT2 gene have been identified as the cause of a variety of early-onset paroxysmal disorders, including benign familial infantile seizure(BFIE), paroxysmal kinesigenic dyskinesia (PKD), infantile convulsions with paroxysmal choreoathetosis(ICCA), hemiplegic migraine and episodic ataxia. We described our BFIE cases caused by PRRT2 mutations and phenotypic variability of their family members with identical genetic mutations.

[Method]: We analyzed ten families with BFIE caused by PPRT2 mutations from August 2013 to April 2018 in Changhua Christian Children’s hospital. PRRT2 mutations were screened by direct PCR and/or array CGH sequencing.

[Result]:A total of 34 affected family members were enrolled from 10 BFIE with PRRT2 mutation families. Among ten probands, 6 with BFIE, 2 with ICCA, 1 with BFIE and infantile mood problem(masturbation), and 1 with BFIE and later occurred endocarditis complicated with encephalitis in teenage. Analysis of PRRT2 mutations of 10 BFIE families found 8 were c.649dupC[p.Arg217Profs*8], 1 with c.323_324delCA[p.Thr108Serfs*25], and 1 with 16p11.2 microdeletion. Among the affected family members, there are 12 cases with BFIE, 4 with PKD, 1 with ICCA, 4 with migraine, 1 with one with young stroke, 2 with late onset epilepsy, respectively.

[Conclusions]:To our best knowledge, young stroke and endocarditis complicated with encephalitis found in our PRRT2 mutation cases are the first report in the literature. We emphasized that aCGH should also be performed in BFIE family especially associated with mood problem. Our report broads the clinical spectrum of phenotypes in PRRT2 mutations of BFIE and their affected family.