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

<bold>Purpose: </bold>De novo truncating mutations of AHDC1 gene cause Xia-Gibbs Syndrome (XGS), characterized by developmental delay, hypotonia, speech disturbances, sleep apnea. Seizures have been reported, yet no studies have depicted the epilepsy characteristics and outcome.<bold>Methods: </bold>We describe the clinical features of a pair of Caucasian monozygotic female twins affected by severe epilepsy and presenting the same de novo AHDC1 mutation detected by whole exome sequencing.<bold>Results: </bold>They were concordant with respect to seizure onset and type mimicking Lennox-Gastaut syndrome as well as initial EEG features, but differed in terms of epilepsy prognosis (complete seizure freedom on valproate/lamotrigine versus ongoing daily refractory seizures despite multiple drug combinations).<bold>Conclusion: </bold>Our findings suggest that patients with Xia-Gibbs Syndrome may exhibit Lennox-Gastaut-like features and that even the same AHDC1 mutation can be poorly predictive of epilepsy prognosis. [ABSTRACT FROM AUTHOR]