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Epilepsy with migrating focal seizures: KCNT1 mutation hotspots and phenotype variability
Giulia Barcia1, Nicole Chemaly1, Mathieu Kuchenbuch1
1Service de Génétique (G.B., J.-P.B., S.G.-L.), Groupe Hospitalier Necker Enfants Malades, Assistance Publique-Hôpitaux de Paris, Paris, France; INSERM U1163 (G.B., N.B-.B., R.N.), Université Paris Descartes, PRES Sorbonne Paris Cité, Paris, France; Service de Neurologie Pédiatrique (N.C., N.B-.B., A.K., R.N.), Hôpital Necker Enfants Malades, Assistance Publique-Hôpitaux de Paris, Paris, France; Centre de Référence des Epilepsies Rares (N.C., A.K., R.N.), Hôpital Necker Enfants Malades, Assistance Publique-Hôpitaux de Paris, Paris, France; INSERM U1129 (N.N., A.K., R.N.), Paris, France; Service de Neurophysiologie Clinique et Pédiatrie (M.K.), INSERM U1099, Hôpital Universitaire de Rennes, Université de Rennes, France; Service de Neurophysiologie Clinique (M.E., A.K.), Hôpital Necker Enfants Malades, Assistance Publique-Hôpitaux de Paris, Paris, France; Service de Génétique Clinique (V.C.), Hôpital Femme Mère Enfant, Metz-Thionville, France; Pediatric Neurology Research Group (A.M.), Vall d'Hebron Research Institute, Universitat Autònoma de Barcelona, Barcelona, Spain; Service de Génétique Clinique (L.L.), Hôpital d'Enfants, CHU de Nancy, Vandoeuvre-Lès-Nancy, France; Service de Pédiatrie (F.D.), CHU de Grenoble, France; Service de Neurologie Pédiatrique (D.D., T.B.V.), Hôpital Trousseau, Assistance Publique-Hôpitaux de Paris, Paris, France; Service de Neurologie Pédiatrique (N.V., M.M.), APHM, Hôpital d'Enfants de La Timone, Marseille, France; Service de Neurologie Pédiatrique (M-.A.B., M.M.), Centre Hospitalier Universitaire de Tours, Tours, France; Département de Génétique (C.N., M.M.), Hôpital Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, Paris, France; Service de Radiologie Pédiatrique (N.B., M.M.), Hôpital Necker Enfants Malades, Assistance Publique-Hôpitaux de Paris, Paris, France; Université Aix-Marseille (M.M.), INSERM, MMG, UMR-S 1251, Faculté de Médecine, Marseille, France; and Unité de Neurologie Pédiatrique (S.A.), Hôpital Rober Debré, Assistance Publique-Hôpitaux de Paris, Paris, France.
Objective:
To report new sporadic cases and 1 family with epilepsy of infancy with migrating focal seizures (EIMFSs) due to KCNT1 gain-of-function and to assess therapies' efficacy including quinidine.
Methods:
We reviewed the clinical, EEG, and molecular data of 17 new patients with EIMFS and KCNT1 mutations, in collaboration with the network of the French reference center for rare epilepsies.
Results:
The mean seizure onset age was 1 month (range: 1 hour to 4 months), and all children had focal motor seizures with autonomic signs and migrating ictal pattern on EEG. Three children also had infantile spasms and hypsarrhythmia. The identified KCNT1 variants clustered as "hot spots" on the C-terminal domain, and all mutations occurred de novo except the p.R398Q mutation inherited from the father with nocturnal frontal lobe epilepsy, present in 2 paternal uncles, one being asymptomatic and the other with single tonic-clonic seizure. In 1 patient with EIMFS, we identified the p.R1106Q mutation associated with Brugada syndrome and saw no abnormality in cardiac rhythm. Quinidine was well tolerated when administered to 2 and 4-year-old patients but did not reduce seizure frequency.
Conclusions:
The majority of the KCNT1 mutations appear to cluster in hot spots essential for the channel activity. A same mutation can be linked to a spectrum of conditions ranging from EMFSI to asymptomatic carrier, even in the same family. None of the antiepileptic therapies displayed clinical efficacy, including quinidine in 2 patients.
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