Humans ; Urea Cycle Disorders, Inborn/diagnosis* ; Ornithine Carbamoyltransferase Deficiency Disease/diagnosis* ; China

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.
Asian Continental Ancestry Group ; Brain Diseases ; Diagnosis ; Genetic Testing ; Genetics ; Humans ; Learning Disorders ; Male ; Mitochondria ; Ornithine ; Paraplegia ; Siblings ; Urea ; Urea Cycle Disorders, Inborn

Diseases of inborn errors of metabolism (IEMs) are very rare but the overall prevalence of IEMs is not low, and in the United States, about 5~10% of admitted patients have some genetic predispositions. Clinical manifestations of IEMs are very diverse, but most frequent manifestations are neurological symptoms and signs. IEMs in Korea have been underestimated because of prejudice, underdevelopment of diagnostic tools and ignorance. The Korean Pediatric Society has done a retrospective study in order to know the relative incidence of IEMs in 2001. All hospitals with over 100 beds participated in the study. The most frequent disease was Wilson disease (201 cases for 10 years) followed by phenylketonuria (98 cases for 10 years) and Hunters disease (69 cases for 10 years). Disorders of mineral metabolism were the most frequently diagnosed disease groups (252 cases for 10 years) followed by organic acidopathies (220 cases), aminoacidopathies (139 cases), mucopolysaccharidosis (131 cases), disorders of carbohydrate metabolism (84 cases), sphingolipidosis (69 cases), urea cycle disorders (39 cases), peroxisomal disorders (27 cases), porphyrias (16 cases), disorders of purine and pyrimidine metabolism (14 cases), disorders of membrane transport (13 cases), fatty acid oxidation disorders (9 cases), oligosaccharidosis (2 cases), and mucolipidosis (1 case). Clearly, Koreans are not protected from IEMs and a systematic approach is needed to make diagnosis more easy and accurate.
Brain Diseases, Metabolic, Inborn ; Carbohydrate Metabolism ; Diagnosis ; Genetic Predisposition to Disease ; Hepatolenticular Degeneration ; Humans ; Incidence ; Korea* ; Membranes ; Metabolism ; Metabolism, Inborn Errors* ; Mucolipidoses ; Mucopolysaccharidoses ; Peroxisomal Disorders ; Phenylketonurias ; Porphyrias ; Prejudice ; Prevalence ; Retrospective Studies ; Sphingolipidoses ; United States ; Urea Cycle Disorders, Inborn

OBJECTIVE: To explore the genetic basis for a Chinese pedigree affected with N-acetylglutamate synthase deficiency. METHODS: Trio whole exome sequencing (WES) was carried out for the pedigree. Pathogenicity of the identified variant was predicted based on the latest recommendation of the American College of Medical Genetics and Genomics (ACMG). Prenatal diagnosis was provided for subsequent pregnancy through Sanger sequencing. RESULTS: Trio WES showed that the proband has carried compound heterozygous c.68delG and c.796G>C variants of NAGS gene, for which the mother and father were respectively heterozygous carriers. Neither variant was reported previously. Based on the ACMG guidelines, the c.68delG variant was classified as "likely pathogenic" (PVS1+PM2), while the c.796G>C variant was classified as with "uncertain significance" (PM2+BP4). Sanger sequencing validated the above findings, and only detected the heterozygous c.796G>C variant in the amniotic fluid sample. The fetus was followed up till 6 month after birth with no obvious abnormality. CONCLUSION The compound heterozygous c.68delG and c.796G>C variants of the NAGS gene probably underlay the disorder in this pedigree, and the resulth asenabled genetic counseling and prenatal diagnosis for this pedigree.
Amino-Acid N-Acetyltransferase/genetics* ; China ; Female ; Genetic Testing ; Humans ; Male ; Mutation/genetics* ; Pedigree ; Pregnancy ; Prenatal Diagnosis ; Urea Cycle Disorders, Inborn/genetics* ; Whole Exome Sequencing

Urea cycle disorders are characterized by encephalopathy, respiratory alkalosis, and hyperammonemia. A urea cycle disorder should be considered a diagnostic possibility in any patient regardless of age with occult encephalopathy. The most common central nervous system pathology of urea cycle disorder is cerebral edema. The cerebral edema is caused by astrocyte swelling secondary to hyperammonemia and intracellular glutamine accumulation. Strokes in children occur in conjunction with cardiac disease, hematologic disorders, mitochondrial encephalopathy, trauma, intracranial infections and migraines. Recently, several inborn errors in metabolism have been recognized as possible causes of stroke. To our knowledge, there have been several reports on ornithine transcarbamylase deficiency with stroke. However, the case of citrullinemia presenting with a stroke-like episode has not been described previously. We report two infantile cases of citrullinemia with initial presentation of stroke. The differential diagnosis of unexplained strokes should include inborn errors of urea cycle metabolism during childhood.
Alkalosis, Respiratory ; Astrocytes ; Brain Edema ; Central Nervous System ; Child ; Citrullinemia* ; Diagnosis, Differential ; Glutamine ; Heart Diseases ; Humans ; Hyperammonemia ; Metabolism ; Migraine Disorders ; Mitochondrial Diseases ; Ornithine Carbamoyltransferase Deficiency Disease ; Pathology ; Stroke* ; Urea ; Urea Cycle Disorders, Inborn

Diagnosis of the urea cycle disorder (USD) carbamoyl-phosphate synthetase 1 (CPS1) deficiency (CPS1D) based on only the measurements of biochemical intermediary metabolites is not sufficient to properly exclude other UCDs with similar symptoms. We report the first Korean CPS1D patient using whole exome sequencing (WES). A four-day-old female neonate presented with respiratory failure due to severe metabolic encephalopathy with hyperammonemia (1,690 µmol/L; reference range, 11.2-48.2 µmol/L). Plasma amino acid analysis revealed markedly elevated levels of alanine (2,923 µmol/L; reference range, 131-710 µmol/L) and glutamine (5,777 µmol/L; reference range, 376-709 µmol/L), whereas that of citrulline was decreased (2 µmol/L; reference range, 10-45 µmol/L). WES revealed compound heterozygous pathogenic variants in the CPS1 gene: one novel nonsense pathogenic variant of c.580C>T (p.Gln194*) and one known pathogenic frameshift pathogenic variant of c.1547delG (p.Gly516Alafs*5), which was previously reported in Japanese patients with CPS1D. We successfully applied WES to molecularly diagnose the first Korean patient with CPS1D in a clinical setting. This result supports the clinical applicability of WES for cost-effective molecular diagnosis of UCDs.
Base Sequence ; Carbamoyl-Phosphate Synthase (Ammonia)/chemistry/*genetics ; Carbamoyl-Phosphate Synthase I Deficiency Disease/diagnosis/*genetics ; Codon, Nonsense ; Exons ; Female ; Frameshift Mutation ; High-Throughput Nucleotide Sequencing ; Humans ; Infant, Newborn ; Republic of Korea ; Sequence Analysis, DNA ; Urea Cycle Disorders, Inborn/diagnosis

OBJECTIVETo explore the molecular mechanism for a boy suspected with 3-methylcrotonyl-CoA carboxylase deficiency by neonatal screening.

METHODSPCR and Sanger sequencing were used to identify potential mutations of MCCC1 and MCCC2 genes. SIFT and Polyphen-2 software was used to predict the effect of variant on the protein function and conservation of the variant across various species. Human Splicing Finder and Swiss-PdbViewer4.1.0 were applied to analyze the possible mechanism of the variant.

RESULTSFor the proband, a compound heterozygous mutation was discovered in the MCCC1 gene, namely c.539G>T (p.G180V) and c.704_711del (p.A235Vfs*4), which were inherited from his father and mother, respectively. The two mutations have disrupted the protein conformation, which in turn may impact the function of MCC protein.

CONCLUSIONThe compound heterozygous mutations of the MCCC1 gene may contribute to the 3-methylcrotonyl-CoA carboxylase deficiency manifested by the patient.

Amino Acid Sequence ; Base Sequence ; Carbon-Carbon Ligases ; chemistry ; deficiency ; genetics ; DNA Mutational Analysis ; Heterozygote ; Humans ; Infant, Newborn ; Male ; Models, Molecular ; Mutation ; Neonatal Screening ; methods ; Protein Conformation ; Sequence Homology, Amino Acid ; Urea Cycle Disorders, Inborn ; diagnosis ; genetics

Amino Acid Transport Systems, Basic ; genetics ; Brain Diseases ; diagnosis ; etiology ; Child ; DNA Mutational Analysis ; Diet, Protein-Restricted ; Female ; Humans ; Hyperammonemia ; complications ; diagnosis ; diet therapy ; genetics ; Ornithine ; deficiency ; genetics ; Recurrence ; Severity of Illness Index ; Urea Cycle Disorders, Inborn ; complications ; diagnosis ; diet therapy ; genetics

OBJECTIVETo report on 5 patients with maternal 3-methylcrotonyl coenzyme A carboxylase deficiency (MCCD) and to confirm the clinical diagnosis through mutation analysis.

METHODSFive neonates with higher blood 3-hydroxy isovalerylcarnitine (C5-OH) concentration detected upon newborn screening with tandem mass spectrometry and their mothers were recruited. Urinary organic acids were analyzed with gas chromatography mass spectrometry. Gene mutation and protein function analysis were performed by PCR direct sequencing and PolyPhen-2 software.

RESULTSHigher blood C5-OH concentrations (5.11-21.77 μmol/L) and abnormal 3-hydroxy isovalerate and 3-methylcrotonyl glycine in urine were detected in the five asymptomatic mothers, who were diagnosed as benign MCCD. Higher C5-OH concentration was also detected in their neonates by tandem mass spectrometry, which had gradually decreased to normal levels in three neonates. Four new variations, i.e., c.ins1680A(25%), c.203C > T (p.A68V), c.572T > C (p.L191P) and c.639+5G > T were detected in the MCCC1 gene, in addition with 2 mutations [c.1406G > T (p.R469L, novel variation) and c.592C > T (p.Q198X)]. The novel variations were predicted to have affected protein structure and function.

CONCLUSIONFor neonates with higher C5-OH concentration detected upon neonatal screening, their mothers should be also tested to rule out MCCD. Mutations in MCCC1 gene are quite common.

Adult ; Amino Acid Sequence ; Base Sequence ; Carbon-Carbon Ligases ; blood ; deficiency ; genetics ; Carnitine ; analogs & derivatives ; blood ; DNA Mutational Analysis ; Female ; Genomic Imprinting ; Humans ; Infant, Newborn ; Male ; Molecular Sequence Data ; Mutation ; Neonatal Screening ; Sex Factors ; Tandem Mass Spectrometry ; Urea Cycle Disorders, Inborn ; blood ; diagnosis ; enzymology ; genetics

OBJECTIVE3-Methylcrotonyl-coenzyme A carboxylase deficiency (MCCD) is an autosomal recessive inborn error of leucine catabolism. The cases suspected as MCCD detected by neonatal screening are not rare. The aim of the study was to investigate the clinical outcomes in cases suspected as MCCD by neonatal screening. The second aim was to investigate the mutation spectrum of MCC gene in Chinese population and hotspot mutation.

METHODForty-two cases (male 33, female 9) , who had higher blood 3-hydroxy-isovalerylcarnitine (C5-OH) levels(cut-off <0.6 µmol/L) detected by neonatal screening using MS/MS, were recruited to this study during Sept.2011 to Mar.2013. The C5-OH concentrations were [0.84 (0.61-20.15) µmol/L] in 42 cases at the screening recall. Five cases were firstly diagnosed as maternal MCCD, 6 cases as benign MCCD and 31 cases were suspected as MCCD. To follow up the height, weight, mental development, blood C5-OH concentrations and urinary 3-methylcrotonyl-glycine (3-MCG) and 3-hydroxy isovalerate (3-HIVA) in order to investigate the clinical outcome. The MCCC1 and MCCC2 gene mutation were analyzed for some cases. The novel gene variants were evaluated, and the influence of novel missense variants on the protein structure and function were predicted by PolyPhen-2, SIFT, UniProt and PDB software.

RESULT(1) Forty-two cases had no symptoms, their physical and mental development were normal in the last visit at the median ages of 29 months, the oldest age of follow up was nearly 9 years. (2) Gene mutation analysis was performed for 29 cases with informed consent signed by parents.Fourteen different mutations were identified in 19 cases. The mutations in MCCC1 gene accounted for 86%, the most common mutation was c.ins1680A, (accounted for 40%). Nine kinds of novel variant were detected including 211AG>CC/p.Q74P, c.295G>A/p.G99S, c.764A>C/p.H255P, c.964G>A/p. E322K, c.1331G>A/p.R444H, c.1124delT, c.39_58del20, c.1518delG, c.639+2T>A.Other 3 kinds of mutation in MCCC1 gene and 2 kinds of mutation in MCCC2 gene have been reported previously; the amino acid of mutant positions of five kinds of novel missense variant are almost highly conserved. These missense variants were predicted to cause change of human MCC protein side chain structure by changing hydrogen bonding, size of amino acid residue and electric charge, and predicted to damage the protein function possibly according to PolyPhen-2 and PDB analysis. So these novel variants may be disease-causing mutations. No mutation were detected in 10 cases. (3) Blood concentrations of C5-OH when screening, recall and end of follow-up in maternal MCCD was 3.50 (1.63-11.43), 1.84 (1.00-9.30), 0.27 (0.26-5.81) µmol/L. There was a significant downward trend.In contrast, benign MCCD group was 8.20 (3.60-9.60), 9.67 (3.88-20.15), 23.0 (5.87-49.10) µmol/L.It showed a rising trend. Children's urinary 3-MCG of benign MCCD group was found abnormally elevated in 4 cases (100%) when they were recalled.

CONCLUSIONA certain number of cases with MCCD or suspected as MCCD in this study had no symptoms and normal physical and mental development after follow-up to oldest age of nearly 9 years. The mutation in MCCC1 gene is common, nine novel mutations were found, c.ins1680A may be a hotspot mutation in Chinese population. The urinary GC/MS analysis and blood MS/MS analysis for mother should be routinely performed for all cases with high blood C5-OH level detected by neonatal screening.

Amino Acid Sequence ; Asian Continental Ancestry Group ; genetics ; Carbon-Carbon Ligases ; blood ; deficiency ; genetics ; Carnitine ; analogs & derivatives ; blood ; Child ; Child, Preschool ; DNA Mutational Analysis ; Female ; Follow-Up Studies ; Humans ; Infant ; Infant, Newborn ; Male ; Mutation ; Neonatal Screening ; Tandem Mass Spectrometry ; Urea Cycle Disorders, Inborn ; blood ; diagnosis ; enzymology ; genetics