Abstract
Coffin-Siris syndrome is a rare multiple congenital anomaly syndrome. We report a case of medically refractory epilepsy developing in a pediatric patient with ARID1B-related Coffin-Siris syndrome, with pachygyria and polymicrogyria in right frontal lobe. Following presurgical evaluations, surgical disconnection of the epileptogenic zone was performed. Postoperative follow-up at 18 months demonstrated complete seizure freedom, with concomitant improvements in speech development and motor strength. This expands the phenotypes associated with ARID1B-related Coffin-Siris syndrome and underscores the importance of early genetic testing for DEEs, along with timely surgical evaluation and treatment for genetic epilepsies where applicable.