Phenotypic spectrum of patients with GABRB2 variants: from mild febrile seizures to severe epileptic encephalopathy

Abstract

Aim: To characterize the different phenotypes of GABRB2-related epilepsy and to establish a genotype–phenotype correlation. Method: We used next-generation sequencing to identify GABRB2 variants in 15 patients. Results: Eleven GABRB2 variants were novel and 12 were de novo. The age at the onset of seizures ranged from 1 day to 26 months. Nine patients had multiple seizure types, including focal seizures, generalized tonic–clonic seizures, myoclonic seizures, epileptic spasms, and atonic seizures. Seizures were fever-sensitive in 13 out of the 15 patients. Eleven patients displayed developmental delay, while 11 had abnormal video electroencephalography. Abnormalities in the brain images included dysplasia of the frontal and temporal cortex, dysplasia of the corpus callosum, and delayed myelination in four patients. One patient was diagnosed with febrile seizures, three with febrile seizures plus, three with Dravet syndrome, three with West syndrome, one with Ohtahara syndrome, three with developmental delays and epilepsy, and one with non-specific early-onset epileptic encephalopathy. Interpretation: The most common phenotypes of patients with GABRB2 variants include early onset of seizure and fever sensitivity. Febrile seizures and febrile seizures plus are new phenotypes of GABRB2 variants. The phenotypic spectrum of GABRB2 variants ranges from mild febrile seizures to severe epileptic encephalopathy.