Early Myoclonic Infantile Encephalopathy in Neonate Caused by 5-Oxoprolinuria, a Rare Metabolic Entity: A Case Report

Abstract

Neonatal encephalopathy is a common entity encountered by treating physicians in any neonatal intensive care unit. Though hypoxic ischaemic encephalopathy is the most frequent cause in developing countries, metabolic causes should also be looked for in refractory neonatal seizures with sibling death and parental consanguinity. Early myoclonic infantile encephalopathy, considered under the broad spectrum of infantile encephalopathy, is a rare syndrome in infants with onset within 3 months of age. It is characterized by myoclonic seizures, features of encephalopathy and caused by underlying metabolic diseases, nonketotic hyperglycinemia being the most common cause. On contrary its close mimicker, Ohtahara syndrome or early infantile epileptic encephalopathy is most likely associated with structural neurological lesions. We report a 12-day term Indian male neonate, born of second degree consanguinity with multiple sibling death history, presented with refractory myoclonic seizures in spite of uneventful birth history. Myoclonic seizures, refractory to intravenous phenobarbitone, phenytoin and infusion Midazolam, persisted after ruling out hypoglycemia, dyselectrolytemia, and neonatal sepsis. EEG showed typical burst suppression pattern pointing towards diagnosis of early myoclonic infantile encephalopathy. Further metabolic causes were looked for but tandem mass spectrometry for dried blood sample was normal. Lastly, urinary GCMS revealed 5-oxoprolinuria, an autosomal recessive condition, characterized by acidosis, jaundice, and severe hemolytic anemia among neonates, primarily due to glutathione synthetase enzyme deficiency. In severe form of 5-oxoprolinuria, neurological complications in form of seizures, ataxia have been documented in earlier studies; however, its association with myoclonic encephalopathy is yet to be reported in the literature and this report may be the first of its kind.