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Nonketotic hyperglycinemia
Published in William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop, Atlas of Inherited Metabolic Diseases, 2020
William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop
Nonketotic hyperglycinemia (glycine encephalopathy) is the second most common inborn error of amino acid metabolism after phenylketonuria. Large amounts of glycine accumulate in body fluids; the increase in CSF is disproportionally high, resulting in an elevated CSF to plasma glycine ratio; and there is no demonstrable accumulation of organic acids. A majority of patients has the classic phenotype in which life-threatening illness begins in the early days of life, and most patients die if not maintained by the use of mechanical ventilation. Survivors usually display little cognitive development and often have virtually continuous seizures. The disease was first described by Gerritsen and colleagues in 1965 [1]. It was called “nonketotic hyperglycinemia” [2, 3] to distinguish it from other disorders, such as propionic acidemia (Chapter 2), in which hyperglycinemia occurs. The high concentration of glycine in CSF and the ratio of its concentration to that of plasma, provide the usual method of diagnosis. Analysis of organic acids of the urine is useful to exclude organic acidemia. Enzyme analysis is not generally available; the enzyme is fully expressed only in the liver and brain.
Metabolic disorders, including glucose homeostasis and inborn errors of metabolism
Published in Janet M Rennie, Giles S Kendall, A Manual of Neonatal Intensive Care, 2013
Janet M Rennie, Giles S Kendall
Glycine encephalopathy presents in the neonatal period with profound hypotonia, coma, apnoea, myoclonic seizures and hiccoughing. Glycine levels are raised in blood and urine, but the increase in cerebrospinal fluid (CSF) levels is particularly striking. A markedly raised CSF–plasma glycine ratio establishes the diagnosis. The enzyme defect can be identified on lymphocytes or liver biopsy. The condition is untreatable, although some authors have claimed improvement with dextromethorphan (an N–methy–D-aspartic acid receptor antagonist).
A pilot study on machine learning approach to delineate metabolic signatures in intellectual disability
Published in International Journal of Developmental Disabilities, 2021
Vidya Nikam, Suvidya Ranade, Naushad Shaik Mohammad, Mohan Kulkarni
The analytes were correlated with demographic characters using Kendall–Tau matrix. 3-Hydroxyisovalerylcarnitine (C5OH) is an indicator for diagnoses of 3-methylcrotonyl-CoA carboxylase deficiency reported to be associated with mild developmental delay (Maeda et al.2008). Decreased levels of acylcarnitines were reported to be associated with neurodegenerative disorders with a major impact on the motor function (Saiki et al.2017). Glutamate results from proline catabolism by aldehyde dehydrogenase and via an aminotransferase enzyme helps in the synthesis of alanine. Glutamate is a main excitatory neurotransmitter and abnormal glutamate signaling is thought to contribute to the pathogenesis of a variety of neurodevelopmental disorders (Fedder and Sabo 2015). This could be explained why subjects with elevated proline and alanine would be having an early onset of ID. Elevated levels of C5 acylcarnitine are characteristic of isovaleric acidemia with clinical features suggestive of significant motor delay (Ensenauer et al.2011). Glycine is an inhibitory neurotransmitter of the central nervous system and its upsurge blood levels are delineated to be a cause of glycine encephalopathy with seizures and speech delay as the major clinical manifestations (Hennermann 2006). The study indicates that Kendall–Tau matrix could efficiently correlate analytes and demographic milestones which match with the reported literature.
Nonketotic Hyperglycinemia: Two Case Reports and Review
Published in The Neurodiagnostic Journal, 2019
Rajesh P. Poothrikovil, Khalid Al Thihli, Amna Al Futaisi, Fathiya Al Murshidi
The infantile form presents in the first few months of life and is also characterized by hypotonia, developmental delay, and seizures. An increased cerebrospinal fluid (CSF) glycine level along with an elevated glycine index (CSF/plasma glycine ratio >0.08) suggests the diagnosis of NKH (Gallagher et al. 2017). EEG typically shows a burst-suppression pattern at the presentation that evolves into multifocal spikes and hypsarrhythmia. MRI can be normal or may show hypoplastic corpus callosum. Although no effective treatment exists for this condition, therapy is focused on managing seizures using antiepileptic medications, reducing the plasma concentration of glycine via administration of sodium benzoate, and N-methyl-D-aspartate (NMDA) receptor antagonism using ketamine injections or oral dextromethorphan. Classical glycine encephalopathy usually carries a very poor prognosis.
A 7-year old female with arthrogryposis multiplex congenita, Duane retraction syndrome, and Marcus Gunn phenomenon due to a ZC4H2 gene mutation: a clinical presentation of the Wieacker-Wolff syndrome
Published in Ophthalmic Genetics, 2021
Deena Godfrey, Alcy Torres, Gena Heidary, Hovra Zahoor, Arthur Lee, Gerard Berry, Elizabeth Engle
Evaluation of congenital disorders of glycosylation, Gaucher type II, and glycine encephalopathy with normal serum glycine was undertaken because these have been associated with AMC (6,8,9). CBC, CMP, and blood lactate, pyruvate, ammonia, and amino acids, and acylcarnitine profile were normal. Two initial blood studies revealed mild elevation in one or several very long chain fatty acids and/or their ratios, while a third follow-up study was normal. Urine oligosaccharides, mucopolysaccharides, organic acids, and acylglycines studies were normal and did not suggest a specific inherited metabolic defect.