A novel AMT gene mutation in a newborn with nonketotic hyperglycinemia and early myoclonic encephalopathy

•Early myoclonic encephalopathy (EME) presents in neonatal period.•Nonketotic hyperglycinemia (NKH) is the most common metabolic cause of EME.•The neurological damage in NKH is caused by NMDA receptor overstimulation.

Early myoclonic encephalopathy (EME) presents in neonatal period with erratic or fragmentary myoclonus and a burst-suppression electroencephalography (EEG) pattern. Nonketotic hyperglycinemia (NKH) is the most common metabolic cause of EME and genetic testing confirms the diagnosis of NKH in around 75% of the patients with a clinical diagnosis of NKH. Three genes are known to cause NKH.Here we describe a case of EME caused by NKH in which a new mutation in aminomethyltransferase (AMT) gene has been detected.