GRIA2 and attention deficit-hyperactivity disorder: Hackmann et al., in 2013 [103], was the first to report a GRIA2 pathogenic variant in a patient presenting with ID, speech delay, gait abnormalities, and ADHD; one other GRIA2 variant was described in an affected child presenting with ID recruited in the Deciphering Developmental Disorders (DDDs) study [102].