Patients with gain-of-function GABRB3 variants presented with a median age of first seizure onset of 2 months [95% confidence interval (CI) 1.6–3], severe to profound intellectual disability (ID) (23/32 patients), epilepsy syndromes described predominantly as unclassified DEEs (16/32), or epilepsy of infancy with migrating focal seizures (EIMFS) (9/32), microcephaly (13/32) and movement disorders including dystonia and dyskinesia (10/32) (Table 1). Here, GABRB3 is linked to epilepsy syndrome.