Early infantile epileptic encephalopathy (EIEE1; OMIM #308350) is the earliest of these age-dependent encephalopathies, manifesting as tonic spasms, myoclonic seizures, or partial seizures, with severely abnormal electroencephalogram, often showing a suppression-burst pattern.
FOXG1 syndrome is as an epileptic-dyskinetic encephalopathy whose clinical presentation bears similarities with ARX- and STXBP1-gene related encephalopathies.
Children's Hospital Boston patient records were retrospectively screened for patients with infantile epileptic encephalopathies who underwent ARX sequencing based on clinical suspicion.
Recently, it has been reported that longer expansions of the polyalanine tract of the ARX gene could cause an early infantile encephalopathy with suppression burst pattern and that the length of this repeat region could be related to the severity of the electroclinical picture.