A phenotypic overlap led to subsequent reports associating FOXG1 mutation with Rett syndrome, a genetic disorder with early onset of neurological symptoms, as both conditions presented with microcephaly, epileptic seizure, hyperkinetic movement, impaired sleep patterns and intellectual disability (Ariani et al., 2008; Mencarelli et al., 2010; Le Guen et al., 2011). Here, FOXG1 is linked to microcephaly.