Benign infantile seizures and paroxysmal dyskinesia caused by an SCN8A mutation

Elena Gardella, Felicitas Becker, Rikke S Møller, Julian Schubert, Johannes R Lemke, Line H G Larsen, Hans Eiberg, Michael Nothnagel, Holger Thiele, Janine Altmüller, Steffen Syrbe, Andreas Merkenschlager, Thomas Bast, Bernhard Steinhoff, Peter Nürnberg, Yuan Mang, Louise Bakke Møller, Pia Gellert, Sarah E Heron, Leanne M DibbensSarah Weckhuysen, Hans Atli Dahl, Saskia Biskup, Niels Tommerup, Helle Hjalgrim, Holger Lerche, Sándor Beniczky, Yvonne G Weber

Publikation: Bidrag til tidsskriftArtikelForskningpeer review

Abstrakt

OBJECTIVE: Benign familial infantile seizures (BFIS), paroxysmal kinesigenic dyskinesia (PKD), and their combination-known as infantile convulsions and paroxysmal choreoathetosis (ICCA)-are related autosomal dominant diseases. PRRT2 (proline-rich transmembrane protein 2 gene) has been identified as the major gene in all 3 conditions, found to be mutated in 80 to 90% of familial and 30 to 35% of sporadic cases.

METHODS: We searched for the genetic defect in PRRT2-negative, unrelated families with BFIS or ICCA using whole exome or targeted gene panel sequencing, and performed a detailed cliniconeurophysiological workup.

RESULTS: In 3 families with a total of 16 affected members, we identified the same, cosegregating heterozygous missense mutation (c.4447G>A; p.E1483K) in SCN8A, encoding a voltage-gated sodium channel. A founder effect was excluded by linkage analysis. All individuals except 1 had normal cognitive and motor milestones, neuroimaging, and interictal neurological status. Fifteen affected members presented with afebrile focal or generalized tonic-clonic seizures during the first to second year of life; 5 of them experienced single unprovoked seizures later on. One patient had seizures only at school age. All patients stayed otherwise seizure-free, most without medication. Interictal electroencephalogram (EEG) was normal in all cases but 2. Five of 16 patients developed additional brief paroxysmal episodes in puberty, either dystonic/dyskinetic or "shivering" attacks, triggered by stretching, motor initiation, or emotional stimuli. In 1 case, we recorded typical PKD spells by video-EEG-polygraphy, documenting a cortical involvement.

INTERPRETATION: Our study establishes SCN8A as a novel gene in which a recurrent mutation causes BFIS/ICCA, expanding the clinical-genetic spectrum of combined epileptic and dyskinetic syndromes.

OriginalsprogEngelsk
Sider (fra-til)428-36
Antal sider9
TidsskriftAnnals of Neurology
Vol/bind79
Udgave nummer3
DOI
StatusUdgivet - mar. 2016

Fingeraftryk Udforsk hvilke forskningsemner 'Benign infantile seizures and paroxysmal dyskinesia caused by an SCN8A mutation' indeholder.

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