Classic Non-ketotic Hyperglycinemia (NKH) in the Neonatal Period：A Case Report

Abstract

This article aims to supplement clinical case data on nonketotic hyperglycinemia (NKH, also known as glycine encephalopathy), an autosomal recessive genetic disorder with an incidence of approximately 1/76,000, which manifests in the neonatal period and has a poor prognosis. The case report involves a 1-day-old preterm male infant admitted due to respiratory distress and poor mental responsiveness. Examination revealed symptoms such as hypotonia and absence of primitive reflexes, along with severe abnormality on electroencephalogram (EEG) and significantly elevated serum and cerebrospinal fluid glycine levels. Whole-exome sequencing identified two potential pathogenic variants in the GLDC gene, consistent with the recessive inheritance pattern of NKH, leading to a definitive diagnosis of glycine encephalopathy. After symptomatic treatment, the parents opted for voluntary discharge due to the poor prognosis. NKH is caused by glycine cleavage enzyme system deficiency leading to glycine accumulation, with 70%-75% of cases attributed to GLDC gene defects.The disease lacks specificity and is prone to misdiagnosis, with currently available treatments showing questionable efficacy. The study calls for in-depth exploration of its pathological mechanisms and therapeutic targets, as well as accumulation of clinical data to improve outcomes for affected children.