Variant Nonketotic Hyperglycinemia Presenting with Elevated Lactate and Pyruvate: A Diagnostic and Management Challenge

Background Non-ketotic hyperglycinemia (NKH) is a rare autosomal recessive metabolic disorder resulting from a defect in the glycine cleavage system, leading to accumulation of glycine in the central nervous system. The classic neonatal form presents as a life-threatening metabolic encephalopathy within the first few days of life. Case Presentation: We report a term neonate, born to a 36-year-old multigravida via third-degree consanguineous marriage, who presented on day 4 of life with poor respiratory effort and shock. There was a history of neonatal seizures on day 3. The infant was intubated and commenced on inotropic support. Recurrent seizures on day 5 necessitated initiation of anticonvulsants (levetiracetam and phenytoin). Given the clinical suspicion of an inborn error of metabolism (IEM), metabolic evaluation revealed significantly elevated plasma glycine levels. Cerebrospinal fluid (CSF) analysis confirmed elevated glycine with an increased CSF-to-plasma glycine ratio (0.19), supporting a diagnosis of NKH. Brain MRI demonstrated features of subacute infarct; MR spectroscopy was unremarkable. Treatment included initiation of high-dose vitamins, with clinical improvement observed. The family was counselled regarding home-based physiotherapy, which was demonstrated and reinforced prior to discharge. Conclusion NKH should be considered in neonates presenting with early-onset seizures and encephalopathy. Diagnosis is supported by elevated CSF glycine levels and an increased CSF/plasma glycine ratio. While definitive diagnosis involves liver biopsy to assess glycine cleavage enzyme activity, supportive treatment with sodium benzoate and NMDA receptor antagonists may help reduce glycine levels and improve outcomes. Early recognition and multidisciplinary support are critical for management.