Different epilepsy course of a novel AHDC1 mutation in a female monozygotic twin pair

•Xia-Gibbs syndrome shows remarkable phenotypic variability and intra-familial heterogeneity.•Although seizures have frequently been reported, the clinical and EEG pattern is till undefined.•Our observation suggest epilepsy may present with Lennox-Gastaut-like features.•Prognosis and response to ASMs may differ even between patients with the same.•mutation.