A male patient with a de novo mutation in the YWHAG gene and mild phenotype is presented. He had normal delivery and normal development, with normal speech and social milestones. At the age of 9 months, myoclonic seizures started, with generalized epileptiform discharges. The child responded well to levetiracetam monotherapy with complete seizure resolution. Levetiracetam was stopped and he remained seizure-free for 10 months. His development was appropriate for age according to psychological evaluation and he attended a regular kindergarten. At the age of approximately 4 years, the seizures reappeared with different semiology of staring with eye blinking. Electroencephalogram (EEG) showed multifocal spikes. Brain magnetic resonance imaging did not reveal any structural abnormality. Genetic analysis revealed a de novo likely pathogenic missense variant in the YWHAG gene (c.619G>A p.Glu207Lys). We compared our case to the other cases published in the literature. Our case is unique in its seizure semiology and evolution of EEG. Moreover, in contrast to our case, the majority of cases described in the literature have dysmorphism and intellectual disability or autistic spectrum disorder. This report emphasizes the phenotypic heterogeneity of YWHAG mutation as is the case in other developmental encephalopathies.
Keywords: YWHAG mutation; developmental and epileptic encephalopathy; early onset myoclonic seizures; phenotypic heterogenity.
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