ARID1A haploinsufficiency has been proposed to cause CSS and intellectual disability (Tsurusaki et al, 2012; Kosho et al, 2013; Santen et al, 2013), but the neurobiological basis for ARID1A‐haploinsufficiency‐related neurodevelopmental disorders remains unknown. The gene discussed is ARID1A; the disease is Intellectual disability.