FOXG1-related disorders, caused by deletions, intragenic mutations or duplications, are usually associated with severe intellectual disability, autistic features, and, in 87% of subjects, epileptiform manifestations.
FOXG1B (forkhead box G1B) is a very intriguing candidate gene since it is known to promote neuronal progenitor proliferation and to suppress premature neurogenesis and its disruption is reported in a patient with postnatal microcephaly, corpus callosum agenesis, seizures, and severe mental retardation.