Developmental and epilepsy spectrum of Poirier–Bienvenu neurodevelopmental syndrome: Description of a new case study and review of the available literature

•Early seizure onset, clustered seizures and delayed development in both males and females are early clinical markers of the disorder.•The most frequently associated seizure types are generalized tonic-clonic and myoclonic seizures.•The severity of neurological impairment is correlated with seizures control. To better characterize the clinical phenotype of Poirier-Bienvenu neurodevelopmental syndrome (OMIM ID: 618,732) due to pathogenic variants of the CSNK2B gene. We reviewed the electro-clinical and developmental data of all 14 patients with de novo mutations of the CSNK2B gene reported in the literature and describe a further individual with a novel CSNK2B pathogenic variant. Clustered generalized tonic-clonic or myoclonic seizures with onset before the age of 18 months and delayed neurodevelopment were present in more than 75% of patients. Epilepsy was pharmaco-resistant in 40%. All the individuals (27%) with normal neurological development had pharmaco-sensitive epilepsy. The severity of cognitive and motor impairments was higher in the group with pharmaco-resistant epilepsy, and a statistically significant correlation between seizure control and the severity of cognitive impairment was documented (χ2(3) = 9.44; p = .024) Early seizure onset, clustered seizures and delayed development in both males and females were early clinical markers in most patients with CSNK2B mutations. The entity of neurodevelopmental abnormalities was related to epilepsy severity. Prospective studies are required to better assess the relationship between epilepsy and developmental outcomes in this condition.