PRRT2 is mutated in familial and non-familial benign infantile seizures

Background: Mutations of protein-rich transmembrane protein 2 (PRRT2) were recently associated to benign familial infantile seizures (BFIS) (MIM 605751) and paroxysmal kinesigenic dyskinesias (PKD) (MIM12800). Aims: To report mutations of PRRT2 in BFIS, infantile convulsions and choreoathetosis (ICCA), and in sporadic cases affected by benign infantile epilepsy (BIE). Methods: A mutational screening of PRRT2 was performed in 5 families, and in 7 sporadic cases affected by BIE. All clinical and neurophysiological details were reviewed. Results: Thirty-three members among 5 families were collected. Fifteen individuals had infantile seizures and one had infantile seizures followed by paroxysmal kinesigenic dyskinesia (PKD). We found the c.649-650InsC PRRT2 mutation in all tested patients (13 out of 15). Age at onset ranged from 3.5 to 10 months. Focal seizures, with or without secondary generalization, occurred mainly in cluster. One patient at the age of 11 years presented with PKD successfully treated with carbamazepine. All patients had a normal cognitive development. Two out of 7 non-familial cases (28.5%) carried a de novo PRRT2 mutation: the c.649-650InsC mutation in one with clustered seizures at the age of 5 months and an unreported c.718C-T p.R240X mutation in the other who, after cluster focal seizures at the age of 5 months, experienced absences at the age of 5 years. Conclusion: Our findings emphasize that PRRT2 mutations might be responsible of both BFIS and ICCA, but might be causative also for sporadic cases of benign infantile seizures. The phenotypic spectrum comprises BFIS, ICCA, and PKD.