Several case-control studies have identified mutations in the GRIN2A gene in patients with different forms of epilepsy, including early-onset epileptic encephalopathy, continuous spike-and-waves during slow-wave sleep syndrome (CSWSS), Landau-Kleffner syndrome (LKS), and Rolandic epilepsy [13,15,18,21–24]. Here, GRIN2A is linked to developmental and/or epileptic encephalopathy with spike-wave activation in sleep.