ATXN1 and attention deficit-hyperactivity disorder: Here, we describe six individuals, five of whom have overlapping interstitial deletions in chromosome 6p22.3-p24.3 encompassing ATXN1. The majority of patients had neurological or behavioral abnormalities, including developmental and speech delay, autism spectrum disorders (ASDs), attention deficit hyperactivity disorder (ADHD), repetitive behaviors, and various dysmorphic features.