Any early infantile epileptic encephalopathy in which the cause of the disease is a mutation in the GABRB1 gene. The disease is developmental and epileptic encephalopathy, 45 (Monarch Disease Ontology identifier MONDO_0014942). Also known as: DEE45, EIEE45, GABRB1 early infantile epileptic encephalopathy, developmental and epileptic encephalopathy 45, early infantile epileptic encephalopathy caused by mutation in GABRB1, epileptic encephalopathy, early infantile, 45, epileptic encephalopathy, early infantile, 45; EIEE45, epileptic encephalopathy, early infantile, type 45.