• Journal of The Korean Society of Inherited Metabolic disease
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• v.5 no.1
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• pp.76-87
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• 2005

Various disorders cause hyperammonemia during childhood. Amongthem are those caused by inherited defects in urea synthesis and related metabolic pathways. These disorders can be grouped into two types: disorders of the enzymes that comprise the urea cycle, and disorders of the transporters or metabolites of theamino acids related to the urea cycle. Principal clinical features of these disorders are caused by elevated levels of blood ammonium. Additional disease-specific symptoms are related to the particular metabolic defect. These specific clinical manifestations are often due to an excess or lack of specific amino acids. Treatment of urea cycle disorders and related metabolic diseases consists of nutritional restriction of proteins, administration of specific amino acids, and use of alternative pathways for discarding excess nitrogen. Although combinations of these treatments are extensively employed, the prognosis of severe cases remains unsatisfactory. Liver transplantation is one alternative for which a better prognosis is reported.

• BMB Reports
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• v.56 no.7
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• pp.385-391
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• 2023

Aspartate-glutamate carrier 2 (AGC2, citrin) is a mitochondrial carrier expressed in the liver that transports aspartate from mitochondria into the cytosol in exchange for glutamate. The AGC2 is the main component of the malate-aspartate shuttle (MAS) that ensures indirect transport of NADH produced in the cytosol during glycolysis, lactate oxidation to pyruvate, and ethanol oxidation to acetaldehyde into mitochondria. Through MAS, AGC2 is necessary to maintain intracellular redox balance, mitochondrial respiration, and ATP synthesis. Through elevated cytosolic Ca²⁺ level, the AGC2 is stimulated by catecholamines and glucagon during starvation, exercise, and muscle wasting disorders. In these conditions, AGC2 increases aspartate input to the urea cycle, where aspartate is a source of one of two nitrogen atoms in the urea molecule (the other is ammonia), and a substrate for the synthesis of fumarate that is gradually converted to oxaloacetate, the starting substrate for gluconeogenesis. Furthermore, aspartate is a substrate for the synthesis of asparagine, nucleotides, and proteins. It is concluded that AGC2 plays a fundamental role in the compartmentalization of aspartate and glutamate metabolism and linkage of the reactions of MAS, glycolysis, gluconeogenesis, amino acid catabolism, urea cycle, protein synthesis, and cell proliferation. Targeting of AGC genes may represent a new therapeutic strategy to fight cancer.

• Neonatal Medicine
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• v.18 no.1
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• pp.143-147
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• 2011

Argininosuccinic aciduria (ASAuria) is a rare autosomal recessive urea cycle disorder. Neonatal presentation of ASAuria is the most common form. It is characterized by lethargy, feeding intolerance, decreased consciousness, and coma after 24 to 72 hours of birth. We describe a rare case of ASAuria in a female neonate who presented with severe hyperammonemia, a typical characteristic of urea cycle disorders. This patient's diagnosis was confirmed by biochemical analyses, and we found that the patient had a point mutation of the argininosuccinate lyase gene, which was homozygous for a novel 556C>T substitution. We have never seen the neonatal form of ASAuria in Korea. Therefore, this is the first report of neonatal onset ASAuria in Korea.

• Journal of The Korean Society of Inherited Metabolic disease
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• v.16 no.2
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• pp.62-69
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• 2016

Newborn screening of some urea cycle disorders has little benefits because of early severe symptoms before the result, low sensitivity (especially hypocitrullinemia) and poor prognosis. But in case of citrullinemia, citrin deficiency and argininosuccinic aciduria diagnosed as elevated citrulline, newborn screening is helpful for early diagnosis and treatment before the symptom. Distinction between the clinical forms of these diseases is based on clinical findings and biochemical results, however, they may not be clearcut. Treatment is different from each other, so exact diagnosis is essential. Here, the diagnostic algorithm for elevated citrulline after tandem mass screening has been proposed. Minimizing total process time from sampling to report of the results is important in Korea for diagnosis and treatment of these disorders.

• Journal of The Korean Society of Inherited Metabolic disease
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• v.18 no.2
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• pp.35-42
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• 2018

Purpose: To follow up Korean patients with metabolic and endocrine disorders ascertained by Korea Genetics Research Center, and assess the long-term effectiveness of extended newborn screening program in Korea. Methods: From January 2000 to December 2017, tandem mass spectrometry and fluoroimmunoassay were employed in extended newborn screening (NBS). The NBS program obtained dried blood spots from 283,626 babies, 48 hours after birth, and screened for galactosemia, congenital hypothyroidism (CH), congenital adrenal hyperplasia (CAH), and 50 preventable inborn errors of amino acid, fatty acid, and organic acid metabolism. Results: 28 cases of amino acid disorders, 75 cases of organic acid disorders, 27 cases of fatty acid disorders, 51 cases of urea cycle disorders, 127 cases of CH, 14 cases of CAH, and 15 cases of galactosemia were ascertained through NBS and subsequent confirmatory laboratory tests. Patients with amino acid metabolic disorders, galactosemia, CH, or CAH were more likely to have a better long-term outcome if detected early. Early management of MSUD led to much better outcome in over 90%. Despite early intervention, 32% of other organic acidemia cases still resulted in developmental delay and neurological problems. Fatty acid disorders showed varied results; those with EMA and MCAD had a good outcome, but those with VLCAD had serious neurological problems and considerably higher mortality. 75% with UCD experienced serious neurological complications and higher mortality. Conclusion: The nation-wide NBS program must be accompanied by comprehensive long-term management and physician and family education of inborn errors of metabolism for a better outcome.

• Journal of the Korean Child Neurology Society
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• v.25 no.3
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• pp.204-207
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• 2017

Hyperornithinemia-hyperammonemia-homocitrullinuria syndrome (HHH syndrome) is a neurometabolic disorder with highly variable clinical severity ranging from mild learning disability to severe encephalopathy. Diagnosis of HHH syndrome can easily be delayed or misdiagnosed due to insidious symptoms and incomplete biochemical findings, in that case, genetic testing should be considered to confirm the diagnosis. HHH syndrome is caused by biallelic mutations of SLC25A15, which is involved in the urea cycle and the ornithine transport into mitochondria. Here we report a boy with spastic paraplegia and asymptomatic younger sister who have compound heterozygous mutations of c.535C>T (p.R179^*) and c.116C>A (p.T39K) in the SLC25A15 gene. We identified that p.T39K mutation is a novel pathogenic mutation causing HHH syndrome and that p.R179^*, which is prevalent in Japanese and Middle Eastern heritage, is also found in the Korean population.

• Journal of The Korean Society of Inherited Metabolic disease
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• v.11 no.1
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• pp.52-73
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• 2011

Since we have started organic acid analysis on Jul. 1997, we have been collecting data about organic acidemias in Korea. The data presented here is our 3 years experience in organic acid analysis. We have collected 712 samples from major university hospitals all over the Korea, large enough for relatively accurate incidence of organic acid disorders. We are using solvent extraction method with ethylacetate, MSTFA for derivatization and quantitation of 83 organic acids simultaneously. Out of 712 patients sample, 498 patients sample (70%) showed no evidence of organic acid abnormalities. Out of 214 remaining samples we have found very diverse disorders such as methylmalonic aciduria(6), propionic aciduria (10), biotinidase deficiency (6), maple syrup urine disease (3), isovaleric aciduria (4), tyrosinemia type II (4), tyrosinemia type IV (1), glutaric aciduria type I (1), glutaric aciduria type II (22), 3-methylglutaconic aciduria type I (3), 3-methylglutaconic aciduria type III (7), HMG-CoA lyase deficiency (1), hyperglyceroluria (2), cytosolic 3-ketothiolase deficiency (55), mitochondrial 3-ketothiolase deficiency (3), 3-hydroxyisobutyric aciduria (2), L-2-hydroxyglutaric aciduria (2), fumaric aciduria (2), lactic aciduria with combined elevation of pyruvate (most likely PDHC deficiency) (28), lactic aciduria without combined elevation of pyruvate (most likely mitochondrial respiratory chain disorders) (35), SCAD deficiency (3), MCAD deficiency (1), 3-methylcrotonylglycineuria (1), orotic aciduria (most likely urea cycle disorders) (7) and 2-methylbranched chain acyl-CoA dehydrogenase deficiency (1). In conclusion, though the incidence of indivisual organic acidemia is low, the incidence of overall organic acidemia is relatively high in Korea. Most of the patients showed some signs of neurological dysfunction. In other words, organic acid analysis should be included in the diagnostic work up of all neurological dysfunctions.

• Clinical and Experimental Pediatrics
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• v.62 no.2
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• pp.43-47
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• 2019

Hyperammonemia can be caused by several genetic inborn errors of metabolism including urea cycle defects, organic acidemias, fatty acid oxidation defects, and certain disorders of amino acid metabolism. High levels of ammonia are extremely neurotoxic, leading to astrocyte swelling, brain edema, coma, severe disability, and even death. Thus, emergency treatment for hyperammonemia must be initiated before a precise diagnosis is established. In neonates with hyperammonemia caused by an inborn error of metabolism, a few studies have suggested that peritoneal dialysis, intermittent hemodialysis, and continuous renal replacement therapy (RRT) are effective modalities for decreasing the plasma level of ammonia. In this review, we discuss the current literature related to the use of RRT for treating neonates with hyperammonemia caused by an inborn error of metabolism, including optimal prescriptions, prognosis, and outcomes. We also review the literature on new technologies and instrumentation for RRT in neonates.

• Journal of The Korean Society of Inherited Metabolic disease
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• v.21 no.1
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• pp.15-21
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• 2021

Purpose: Urea cycle disorder (UCD) is an inherited inborn error of metabolism, acting on each step of urea cycle that cause various phenotypes. The purpose of the study was to investigate the long-term clinical consequences in different groups of UCD to characterize it. Methods: Twenty-two patients with UCD genetically confirmed were enrolled at Pusan National University Children's hospital and reviewed clinical features, biochemical and genetic features retrospectively. Results: UCD diagnosed in the present study included ornithine transcarbamylase deficiency (OTCD) (n=10, 45.5%), argininosuccinate synthase 1 deficiency (ASSD) (n=6, 27.3%), carbamoyl-phosphate synthetase 1 deficiency (CPS1D) (n=3, 13.6%), hyperornithinemia-hyperammonemia-homocitrullinuria syndrome (HHHS) (n=2, 9.1%), and arginase-1 deficiency (ARG1D) (n=1, 4.5%). The age at the diagnosis was 32.7±66.2 months old (range 0.1 to 228.0 months). Eight (36.4%) patients with UCD displayed short stature. Neurologic sequelae were observed in eleven (50%) patients with UCD. Molecular analysis identified 37 different mutation types (14 missense, 6 nonsense, 6 deletion, 6 splicing, 3 delins, 1 insertion, and 1 duplication) including 14 novel variants. Progressive growth impairment and poor neurological outcomes were associated with plasma isoleucine and leucine concentrations, respectively. Conclusion: Although combinations of treatments such as nutritional restriction of proteins and use of alternative pathways for discarding excessive nitrogen are extensively employed, the prognosis of UCD remains unsatisfactory. Prospective clinical trials are necessary to evaluate whether supplementation with BCAAs might improve growth or neurological outcomes and decrease metabolic crisis episodes in patients with UCD.

• Journal of The Korean Society of Inherited Metabolic disease
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• v.16 no.3
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• pp.123-134
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• 2016

Mitochondrial disease is a group of disorders caused by dysfunctional mitochondria, the organelles that generate energy for the cell. Diagnosis of mitochondrial disease is difficult, subtle, and has many problems. It is more likely to miss the diagnosis of mitochondrial disease, especially in borderline cases where the symptoms of the disease are not severe. In this regard, urine organic acid analysis is noninvasive and can increase the sensitivity and specificity through repeated load test with few changes according to the specimen. And, It is considered to be suitable as a screening test for mitochondrial diseases because it has a great advantage of distinguishing from organic aciduria, urea cycle disorder and fatty acid oxidation disorder which may have similar symptoms. The purpose of this study was to investigate the clinical features and age distribution of mitochondrial diseases diagnosed by organic acid analysis and to establish the policy of diagnosis and treatment based on this study.