OBJECTIVE: To analyze the clinical phenotype and genetic basis for a child with acute form of tyrosinemia type I (TYRSN1). METHODS: A child with TYRSN1 who presented at the Gansu Provincial Maternal and Child Health Care Hospital in October 2020 was selected as the subject. The child was subjected to tandem mass spectrometry (MS-MS) and urine gas chromatography-mass spectrometry (GC-MS) for the detection of inherited metabolic disorders, in addition with whole exome sequencing (WES). Candidate variants were validated by Sanger sequencing. RESULTS: The child's clinical features included abdominal distension, hepatomegaly, anemia and tendency of bleeding. By mass spectrometry analysis, her serum and urine tyrosine and succinylacetone levels have both exceeded the normal ranges. WES and Sanger sequencing revealed that she has harbored c.1062+5G>A and c.943T>C (p.Cys315Arg) compound heterozygous variants of the FAH gene, which were inherited from her father and mother, respectively. Among these, the c.943T>C was unreported previously. CONCLUSION Considering her clinical phenotype and result of genetic testing, the child was diagnosed with TYRSN1 (acute type). The compound heterozygous variants of the FAH gene probably underlay the disease in this child. Above finding has further expanded the spectrum of FAH gene variants, and provided a basis for accurate treatment, genetic counseling and prenatal diagnosis for her family.
Female ; Humans ; Gas Chromatography-Mass Spectrometry ; Genetic Testing ; Mutation ; Phenotype ; Prenatal Diagnosis ; Tyrosinemias/genetics* ; Child

OBJECTIVETo analyze clinical data and gene mutations in 3 Chinese patients with tyrosinemia type I, and to explore the correlation between genotypes and phenotypes.

METHODSThree patients suspected with tyrosinemia I were tested by tandem mass spectrometry for the level of tyrosine, phenylalanine and succinylacetone in the blood, and by gas chromatography-mass spectrometry to determine the level of succinylacetone and organic acid in their urine. With the diagnosis established, the FAH gene was analyzed with polymerase chain reaction (PCR) and direct sequencing.

RESULTSTwo patients had acute onset of the disease, while another had subacute onset of the disease, with features including hepatomegaly and remarkably increased tyrosine and succinylacetone in the blood. Five mutations were detected in the FAH gene, which included c.455G>A (W152X), c.520C>T (R174X), c.974_976delCGAinsGC, c.1027 G>A (G343R) and c.1100 G>A (W367X), among which c.455G>A (W152X), c.974_976delCGAinsGC and c.1100 G>A (W367X) were not reported previously.

CONCLUSIONTyrosinemia type I may be effectively diagnosed with the level of tyrosine and succinylacetone by tandem mass spectrometry and succinylacetone in the urine by gas chromatography mass spectrometry. Detection of underlying mutations mutations will be helpful for genetic counseling and further research.

Asian Continental Ancestry Group ; genetics ; Base Sequence ; China ; Female ; Humans ; Hydrolases ; genetics ; Infant ; Male ; Mutation ; Tyrosinemias ; diagnosis ; genetics

BACKGROUNDMutations in fumarylacetoacetate hydrolase (FAH) gene can lead to tyrosinemia type 1 (HT1), a relatively rare autosomal recessive disorder. To date, no molecular genetic defects of HT1 in China have been described. We investigated a Chinese family with a HT1 child to identify mutations in FAH.

METHODSDNA sequencing was used for mutations screening in FAH gene. Real-time polymerase chain reaction (PCR) was performed to determine the FAH gene expression level. To confirm the presence of degradation by the nonsense-mediated mRNA decay pathway (NMD), the fragments containing R237X mutations were analyzed by primer introduced restriction analysis-polymerase chain reaction (PIRA-PCR) and cDNA sequencing. Finally, the effects of the mutations reported in this study were predicted by online softwares.

RESULTSA boy aged 3 years and 8 months was diagnosed clinically with HT1 based on his manifestations and biochemical abnormalities. Screening of FAH gene revealed two heterozygous mutations R237X and L375P transmitted from his mother and father respectively. In this pedigree, the amount of FAH mRNA relative to a healthy control was 0.44 for the patient, 0.77 for his mother and 1.07 for his father. Moreover, both PIRA-PCR and cDNA sequencing showed significant reduction of the FAH mRNA with R237X nonsense mutation. The missense mutation of L375P was not reported previously and prediction software showed that this mutation decreased the stability of protein structure and affected protein function.

CONCLUSIONSThis is the first case of HT1 analyzed by molecular genetics in China. The R237X mutation in FAH down- regulates the FAH gene expression, and the L375P mutation perhaps interrupts the secondary structure of FAH protein.

Child, Preschool ; China ; Humans ; Hydrolases ; genetics ; Male ; Molecular Sequence Data ; Mutation ; Mutation, Missense ; genetics ; Nonsense Mediated mRNA Decay ; genetics ; Real-Time Polymerase Chain Reaction ; Tyrosinemias ; genetics

OBJECTIVE: To analyze the results of screening for hereditary tyrosinemia (HT) in newborns and its clinical features and genotype. METHODS: The HT screening was conducted among 2 188 784 newborns from November 2013 to November 2018. The tyrosine (TYR)/ succinylacetone (SA) levels were detected by tandem mass spectrometry (MS-MS). The clinical characteristics, genetic results and following up data of identified patients were analyzed. RESULTS: The normal ranges (0.5%-95.5%) of TYR and SA were 34.5-280.0 μmol/L and 0.16-2.58 μmol/L, respectively. Three HT cases were confirmed with a detection rate of 1∶729 595. There was 1 case of tyrosinemia type Ⅰ (HTⅠ) (homozygous variations of c.455G>A in gene), 1 case of tyrosinemia type Ⅱ(HTⅡ) (heterozygous variations of c.890G>T and c.408+1G>A in gene), and 1 case of tyrosinemia type Ⅲ (HT Ⅲ) (homozygous variations of c.257T>C in gene). The variations of c.890G>T, c.4081G>A of and c.257T>C of were novel. The positive predictive value of the screening was 3.4%. Case 1 (HTⅠ) with TYR and SA values of 666.9 μmol/L and 3.87 μmol/L respectively, presented cholestasis, mild elevated of liver enzyme and lactic acid, who were although fed with TYR and phenylalanine free milk, but died at 2 months of age. Case 2 (HTⅡ) with higher TYR (625.6 μmol/L) and normal SA at screening, received medical milk treatment; during the 7 months of follow-up the baby showed normal score of Bayley assessment and normal TYR without eye and skin symptoms. Case 3 (HT Ⅲ) with TYR of 1035.3 μmol/L and normal SA at screening; during the 29 months of follow-up the value of TYR fluctuated from 532.1 μmol/L to 1060.3 μmol/L due to irregular medical milk treatment, while the score of Bayley assessment was normal. CONCLUSIONS HT is rare in the southern Chinese population, and the gene spectrum is scattered. Early treatment with nitisinone is recommended in children with HTⅠ, otherwise the prognosis is poor; the prognosis of children with HTⅡ is good when early treated with special diet; the prognosis of children with HTⅢ needs to be determined with more data.
Child ; Cyclohexanones ; therapeutic use ; Genotype ; Humans ; Infant ; Infant, Newborn ; Neonatal Screening ; Nitrobenzoates ; therapeutic use ; Tandem Mass Spectrometry ; Tyrosinemias ; diagnosis ; drug therapy ; genetics

OBJECTIVETo investigate the clinical features and mutations of the FAH gene.

METHODClinical records of two cases were collected, and diagnosis was made according to the diagnostic criteria of the International Organization for Rare Disorders (NORD). Genomic DNA was extracted from peripheral blood leukocytes with QIAamp DNA Mini Kit. The DNA extracts were subjected to direct sequencing for 14 exons together with adjacent fragments of FAH gene using ABI Prism 3730 Genetic Analyzer (Applied Biosystems, Foster City, CA) after PCR based on genomic DNA. The mutation source was verified by analyzing parents' exons corresponding to patients' mutation exons. The homology between human FAH enzyme and that of other species was surveyed using software Clustal X(European Bioinformatics Institute, Hinxton, Saffron Walde, UK). Polyphen (Polymorphism Phenotyping), available online, were used to predict possible impact of an amino acid substitution on structure and function of FAH enzyme. Polyphen calculates position-specific independent counts (PISC) scores for two amino acid variants in polymorphic position. A PISC scores that differ by > 2 were regarded as indicating the probability of damaging variants.

RESULTPatient 1 was a 5 months and 21 days-old boy who suffered from persistent diarrhea, hepatomegaly, ascites; Alpha-fetoprotein > 1210 µg/L, levels of tyrosine in blood and succinylacetone in urine were 110.8 µmol/L and 83.7 µmol/L. His sister suffered from tyrosinemia type 1. Direct sequencing showed a G to A transition in CDS position 455 and 1027. He was compound heterozygous for the mutation c.455G > A/c.1027G > A, which predicts a change from tryptophan to a stop codon (TGG > TAG) at position 152 (W152X) and a change from glycine to arginine (GGG > AGG) at position 343 respectively. Patient 2 was a 6 year and 1 month-old girl with late-onset rickets who had signs of hepatosplenomegaly, rachitic rosary, windswept knees. Hypophosphatemia and alkaline phosphatase 1620 IU/L were detected. Alpha-fetoprotein 412.8 µg/L, levels of tyrosine in blood and succinylacetone in urine were 835.8 µmol/L and 27.48 µmol/L. Rickets did not improve after administration of calcium and vitamine D3. She is homozygous for the mutation c.1027G > A/c.1027G > A, which predicts G343R. The parents were mutation carriers. Analysis by Clustal X on the alignment of amino acids residual reservation among different species showed that the locative amino acid was highly conserved. Polyphen software predicted G343R was probably damaging (PISC score 3.235).

CONCLUSIONChildren with tyrosinemia type 1 can have manifestations of persistent diarrhea or late-onset rickets. Physical examination can reveal hepatosplenomegaly, laboratory tests indicate markedly elevated serum concentration of alpha-fetoprotein and alkaline phosphatase in plasma and succinylacetone in urine, other members in family may have tyrosinemias or parents are consanguineous. Mutations c.455G > A and c.1027G > A can be detected in FAH gene of Chinese children.

Amino Acid Sequence ; Base Sequence ; Child ; Child, Preschool ; DNA Mutational Analysis ; Diarrhea ; etiology ; genetics ; Exons ; Female ; Heptanoates ; urine ; Humans ; Hydrolases ; genetics ; Infant ; Male ; Mutation ; Pedigree ; Polymerase Chain Reaction ; Rickets ; etiology ; genetics ; Tyrosine ; blood ; Tyrosinemias ; complications ; diagnosis ; genetics ; pathology ; alpha-Fetoproteins ; analysis