We report the first inherited ARF1variant in a girl with intellectual disability and periventricular nodular heterotopia, and in her father with previously undiagnosed single nodular heterotopia and mild clinical expression. Additionally, our patients presente some features suggestive for hypohidrotic ectodermal dysplasia. The clinical features of our patients showed similarities to those of three previously reported cases with ARF1 missense variants, confirming that haploinsufficiency of this gene causes a recognizable neurological disorder with abnormal neuronal migration and variable clinical expressivity. (By Antonella Casella, https://jmg.bmj.com/content/early/2021/08/04/jmedgenet-2021-107783 )