Additional observation of a de novo pathogenic variant in KCNT2 leading to epileptic encephalopathy with clinical features of frontal lobe epilepsy

Introduction: KCNT2 was recently recognized as a gene associated with neurodevelopmental disorder and epilepsy. Case report: We present an additional observation of a 16-year-old male patient with a novel de novo KCNT2 likely pathogenic variant and review the five previously reported cases of de novo variants in this gene. Discussion: Whole exome sequencing identified the missense variant c.725C > A p.(Thr242Asn), which was confirmed by Sanger sequencing. Our patient has a refractory stereotyped and monomorphic type of hyperkinetic focal motor seizure, similar to what is seen in frontal lobe epilepsy, occurring only during sleep. This type of seizure is not usually seen in epileptic encephalopathies. (C) 2020 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.