Pitfalls in the diagnosis of glycine encephalopathy (non‐ketotic hyperglycinemia)

Pitfalls in the diagnosis of glycine encephalopathy (non‐ketotic hyperglycinemia) Non-ketotic hyperglycinemia (NKH), also termed glycine encephalopathy (MIMa 605899), is an autosomal recessive inborn error of glycine degradation which leads to severe neurological symptoms and profound psychomotor disability. In NKH, glycine accumulates in all body fluids and tissues, including the CNS. The biochemical hallmark of NKH is increased glycine concentration in the plasma and to an even greater extent in the CSF, leading to an elevation of the CSF:plasma glycine ratio (C:PGR) to above 0.08 (normal <0.04). The fundamental defect is in the glycine cleavage system (GCS), a multienzyme complex located in the inner mitochondrial membrane of the liver, kidney, brain, and placenta. It consists of four individual protein components termed P (a pyridoxal phosphate-dependent glycine decarboxylase), H (a lipoic acid-containing hydrogen carrier protein), T (a tetrahydrofolate-dependent protein), and L (a lipoamide dehydrogenase). In more than 80% of patients the defect is in the P protein (MIM 238300), but defects in the T (MIM 238310) and H (MIM 238330) proteins have also been described. The pathogenesis of NKH is related to the properties of glycine as an excitatory neurotransmitter acting via the N-methyl-Daspartate receptor in the cortex and an inhibitory neurotransmitter in the brainstem and spinal cord.1–3 Classically, http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Developmental Medicine & Child Neurology Wiley

Pitfalls in the diagnosis of glycine encephalopathy (non‐ketotic hyperglycinemia)

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Publisher
Wiley
Copyright
Copyright © 2002 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0012-1622
eISSN
1469-8749
DOI
10.1111/j.1469-8749.2002.tb00275.x
Publisher site
See Article on Publisher Site

Abstract

Non-ketotic hyperglycinemia (NKH), also termed glycine encephalopathy (MIMa 605899), is an autosomal recessive inborn error of glycine degradation which leads to severe neurological symptoms and profound psychomotor disability. In NKH, glycine accumulates in all body fluids and tissues, including the CNS. The biochemical hallmark of NKH is increased glycine concentration in the plasma and to an even greater extent in the CSF, leading to an elevation of the CSF:plasma glycine ratio (C:PGR) to above 0.08 (normal <0.04). The fundamental defect is in the glycine cleavage system (GCS), a multienzyme complex located in the inner mitochondrial membrane of the liver, kidney, brain, and placenta. It consists of four individual protein components termed P (a pyridoxal phosphate-dependent glycine decarboxylase), H (a lipoic acid-containing hydrogen carrier protein), T (a tetrahydrofolate-dependent protein), and L (a lipoamide dehydrogenase). In more than 80% of patients the defect is in the P protein (MIM 238300), but defects in the T (MIM 238310) and H (MIM 238330) proteins have also been described. The pathogenesis of NKH is related to the properties of glycine as an excitatory neurotransmitter acting via the N-methyl-Daspartate receptor in the cortex and an inhibitory neurotransmitter in the brainstem and spinal cord.1–3 Classically,

Journal

Developmental Medicine & Child NeurologyWiley

Published: Oct 1, 2002

References

  • Transient neonatal hyperglycinemia
    Schiffmann, Schiffmann; Kaye, Kaye; Willis, Willis; Africk, Africk; Ampola, Ampola

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