EC Clinical and Medical Case Reports

Nonketotic hyperglycinemia (NKH), or glycine encephalopathy, is a rare inherited metabolic disorder transmitted in an autosomal recessive manner. It results from a defect in the glycine cleavage system, leading to an excessive accumulation of glycine in plasma and cerebrospinal fluid. This accumulation causes overstimulation of NMDA receptors and severe neurological manifestations.

We report three neonatal cases consistent with the classical severe form. The newborns presented with profound hypotonia, intractable seizures, marked lethargy, and early apnea. The diagnosis was confirmed by elevated plasma and CSF glycine levels with an increased CSF/plasma ratio, together with characteristic electroencephalographic findings showing a suppression-burst pattern.

The clinical course was rapidly unfavorable in all three cases, with early neonatal death despite intensive resuscitation measures.

These observations highlight the severity of neonatal NKH, underline the importance of early diagnosis and multidisciplinary evaluation, and emphasize the role of genetic counseling for affected families. They also reinforce the urgent need for innovative therapeutic strategies to improve the prognosis of this rare but devastating disorder.

Keywords: Nonketotic Hyperglycinemia; Inborn Errors of Metabolism; Pediatric Neurology; Genetic Disorders

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