Identification of predominant GNPTAB gene mutations in Eastern Chinese patients with mucolipidosis II/III and a prenatal diagnosis of mucolipidosis II.

Mucolipidosis II α/ß, mucolipidosis III α/ß, and mucolipidosis III γ are autosomal recessive disorders belonging to the family of lysosomal storage disorders caused by deficiency of the UDP-N-acetylglucosamine, a lysosomal enzyme N-acetylglucosamine-1-phosphotransferase (GlcNAc-phosphotransferase) localized in the Golgi apparatus, which is essential for normal processing and packaging of soluble lysosomal enzymes with initiating the first step of tagging lysosomal enzymes with mannose-6-phosphate (M6P). Mucolipidosis II and III are caused by mutations in the GNPTAB and GNPTG genes, and patients with these diseases are characterized by short stature, skeletal abnormalities, and developmental delay. In this study we report 38 patients with mucolipidosis II and III enrolled in Eastern China during the past 8 years. The diagnosis was made based on clinical characteristics and measurement of plasma lysosomal enzyme activity. Sanger sequencing of GNPTAB and/or GNPTG for all patients and real-time quantitative PCR were performed to confirm the diagnosis. In addition, 11 cases of prenatal mucolipidosis II were diagnosed based on measurement of the enzyme activity in amniotic fluid supernatant and genetic testing of cultured amniotic cells. Based on molecular genetic tests, 30 patients were diagnosed with mucolipidosis II α/ß, 6 were diagnosed with III α/ß and 2 were diagnosed with III γ. Thirty-seven different GNPTAB gene mutations were identified in 29 patients with mucolipidosis II α/ß and six patients with III α/ß. These mutations included 22 new mutations (p.W44X, p.E279X, p.W416X, p.W463X, p.Q802X, p.Q882X, p.A34P, p.R334P, p.D408N, p.D534N, p.Y997C, p.D1018V, p.L1025S, p.L1033P, c.88_89delAC, c.890_891insT, c.1150_1151insTTA, c.1523delG, c.2473_2474insA, c.2980_2983delGCCT, c.3094delA, and deletion of exon 9). Four new GNPTG gene mutations were identified (c.13delC, p.Y81X, p.G126R and c.609+1delG) in two mucolipidosis III γ patients. Among the 11 cases of prenatal diagnosis, four were mucolipidosis II fetuses, three were heterozygous, and the remaining four were normal fetuses. This study expands the mutation spectrum of the GNPTAB and GNPTG genes and contributes to specific knowledge of mucolipidosis II/III in a population from Eastern China.

A Functional Mutation in HDAC8 Gene as Novel Diagnostic Marker for Cornelia De Lange Syndrome.

BACKGROUND/AIMS: Cornelia de Lange Syndrome (CdLS) is a rare genetic disorder classically characterized by distinctive facies, growth retardation, intellectual disability, feeding difficulties, and multiple organ system anomalies. Previously, the diagnosis of CdLS was based mainly on identifying the typical phenotype in patients. However, with the advances in clinical molecular genetic diagnostic techniques, more patients, especially patients with milder phenotypes, are being diagnosed from detecting pathogenic mutation. METHODS: Pathogenic mutation in a female patient with a milder phenotype was detected using whole-exome sequencing (WES), and was further characterized using bioinformatic analysis and in vitro functional experiments, including X-chromosome inactivation analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and enzyme activity assay. RESULTS: This patient was found to harbor a novel missense mutation (c.806T>G, p.I269R) in the coding region of the HDAC8 gene, which was predicted to be pathogenic. Compared with other CdLS patients with HDAC8 mutation, the patient lacked typical facies, including synophrys and arched eyebrows. In vitro functional experiments showed the presence of skewed X-chromosome inactivation. Furthermore, the novel mutation decreased the dissolubility and enzymatic activity of HDAC8 protein. CONCLUSIONS: The present study identified a novel missense mutation (c.806T>G, p.I269R) in the HDAC8 gene leading to CdLS, which not only provided strong evidence for diagnosis in this present patient, but also expanded the spectrum of pathogenic mutations for CdLS.

Genetic Evaluation of 114 Chinese Short Stature Children in the Next Generation Era: a Single Center Study.

BACKGROUND/AIMS: The genetics of human height is a frequently studied and complex issue. However, there is limited genetic research of short stature. To uncover the subgroup of patients to have higher yield and to propose a simplified diagnostic algorithm in the next generation era. METHODS: This study included 114 Chinese children with height SDS ≤ -2.5 and unknown etiology from 2014 to 2015. Target/whole exome sequencing (referred as NGS) and chromosomal microarray analysis (CMA) were performed on the enrolled patients sequentially to identify potential genetic etiologies. The samples solved by NGS and CMA were retrospectively studied to evaluate the clinical pathway of the patients following a standard diagnostic algorithm. RESULTS: In total, a potential genetic etiology was identified in 41 (36%) patients: 38 by NGS (33.3%), two by CMA (1.8%), and an additional one by both (0.9%). There were 46 different variants in 29 genes and 2 pathogenic CNVs identified. The diagnostic yield was significantly higher in patients with facial dysmorphism or skeletal abnormalities than those without the corresponding phenotype (P=0.006 and P=0.009, respectively, Pearson's χ2 test). Retrospectively study the cohort indicate 83.3% patients eventually would be evaluated by NGS/CMA. CONCLUSION: This study confirms the utility of high-throughput molecular detection techniques for the etiological diagnosis of undiagnosed short stature and suggests that NGS could be used as a primary diagnostic strategy. Patients with facial dysmorphism and/or skeletal abnormalities are more likely to have a known genetic etiology. Moving NGS forward would simplified the diagnostic algorithm.

[Efficacy and safety of a phenylalanine-free amino acid-based enteral formula (AA-PKU2) in 1-8 year-old children with phenylketonuria: a prospective, open, self-controlled and multi-center study in China].

OBJECTIVE: To evaluate the efficacy and safety of a phenylalanine-free amino acid-based enteral formula (AA-PKU2) in the treatment of children with phenylketonuria (PKU) aged 1-8 years. METHODS: A prospective, open, self-controlled, multi-center trial was performed, enrolling 121 PKU children (1-8 years in age) consecutively between July, 2009 and May, 2011. Enteral nutrition therapy was administered for 32 weeks. The data on blood phenylalanine (PHE) levels, metal development, weight, height, head circumference, serum nutritional biomarkers (total protein, pre-albumin, albumin, total cholesterol, total triglyceride, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol), and measurements from routine blood and urine examinations and from renal and hepatic function tests were collected before the therapy and at 8 weeks and 32 weeks after the therapy and were comparatively analyzed. RESULTS: The mean blood PHE level at 8 and 32 weeks of AA-PKU2 treatment was 353±253 and 361±280 µmol/L respectively, significantly lower than that before the treatment (487±327 µmol/L; P<0.01). The difference in intelligence quotient scores before and after AA-PKU2 treatment was not significant (P>0.05) when assessed by the Gesell tests in children aged 1-4 years but significant (P<0.01) when assessed by WPPSI or WISR-R tests in children over 4 years. The average height, weight and head circumference at 8 and 32 weeks after treatment were significantly increased as compared to these measurements before treatment (P<0.01) with absolute levels similar to those in the control children. In contrast, the mean values of total protein, pre-albumin, albumin, total cholesterol, total triglyceride, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol at both time points were not different either from those prior to the treatment or from those in the control children. Mild diarrhea was the adverse events associated with AA-PKU2 treatment, which occurred in 3 (2.5%) cases. All these 3 patients fully recovered without treatment. CONCLUSIONS: The phenylalanine-free amino acid-based formula, AA-PKU2, is effective and safe in controlling blood PHE levels and improving mental development with adequate nutritional support in PKU.

[In vitro expression study of novel mutations in phenylalanine hydroxylase gene].

OBJECTIVE: To study the in vitro expression of 6 novel missense mutations (R270G, P275A, F121L, A156P, E183G, I324N) and a previously described R408Q mutation of phenylalanine hydroxylase (PAH) gene and explore the genotype-phenotype correlation through comparison of protein levels and residual enzyme activities. METHODS: Seven expression vectors containing PAH cDNA were constructed with a site-directed mutagenesis kit. The plasmids were extracted and sequenced to confirm the target mutations. pcDNA3.0 containing PAH cDNA was transfected into COS-7 cells and total proteins were extracted 48 h after transfection. The quantities of proteins and residual enzyme activities of the 7 mutants were assessed with the wild-type PAH gene as reference. RESULTS: Relative quantities of PAH proteins for R270G, P275A, F121L, A156P, E183G, I324N and R408Q were 10.5%, 56.6%, 54.3%, 8.7%, 8.5%, 67.3% and 85.4%, respectively. The residual enzyme activities were 7.7%, 27.6%, 19.0%, 10.4%, 9.1%, 50.6% and 40.2%, respectively. CONCLUSION: PAH residual enzyme activities of 7 PAH mutants were all significantly reduced.

[Clinical and mutational features of maternal 3-methylcrotonyl coenzyme deficiency].

OBJECTIVE: To report on 5 patients with maternal 3-methylcrotonyl coenzyme A carboxylase deficiency (MCCD) and to confirm the clinical diagnosis through mutation analysis. METHODS: Five 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. RESULTS: Higher 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. CONCLUSION: For 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.

[Diagnosis and treatment of isolated methylmalonic acidemia].

OBJECTIVE: To explore the clinical feature, therapeutic effect and prognosis of isolated methylmalonic acidemia. METHODS: The clinical characteristics, laboratory findings, treatment and outcome of 40 patients were retrospectively analyzed. The main treatment was a low-protein diet supplemented with L-carnitine and special milk free of leucine, valine, threonine and methionine. Vitamin B12 was also given to cobalamin responders. The patients were followed up every 1-3 months. RESULTS: Mutations in the MUT gene were identified in 30 of 33 patients who had accepted DNA testing. Thirty cases were treated and followed up regularly for from 1 month to 8 years. Eight cases had died, 8 had developed normal intelligence, among whom 4 from newborn screening were asymptomatic. Psychomotor developmental delay and mental retardation were present in 14 cases. The propionylcarnitine level, ratio of propionylcarnitine/acetylcarnitine in blood, methylmalonic acid and methylcitric acid levels in urine have decreased significantly, with the median values reduced respectively from 24.15 (7.92-81.02) µmol/L, 1.08 (0.38-6.01), 705.34 (113.79-3078.60) and 7.71 (0.52-128.21) to 10.50 (3.00-30.92) µmol/L, 0.63 (0.25-2.89), 166.23 (22.40-3322.21) and 3.96 (0.94-119.13) (P < 0.05). CONCLUSION: The prognosis of isolated methylmalonic acidemia may be predicted with the enzymatic subgroup, age at onset and cobalamin responsiveness. Outcome is unfavorable in neonatal patients and those who were non-responsive to cobalamin.

[Analysis of propionylcarnitine in blood and methylmalonic acid in urine of 162 patients with methylmalonic acidemia].

OBJECTIVE: To analyze the levels of methylmalonic acid and methylcitrate in urine, propionylcarnitine (C3) in plasma and C3/acetylcarnitine (C2) of patients with methylmalonic acidemia (MMA) and explore their applications in the diagnosis of MMA. METHODS: From December 2003 to March 2012, a total of 162 patients with MMA (MMA group) and 200 healthy children (control group) of Xinhua Hospital, Shanghai Jiaotong University School of Medicine were recruited. MMA patients with a definite classification were divided into 2 groups: isolate MMA group (n = 51) and MMA complicated with homocysteinemia group (n = 65). Gas chromatography-mass spectrometry was used to measure the urine levels of methylmalonic acid and methylcitrate and tandem mass spectrometry to measure the blood levels of free carnitine (C0), acylcarnitines and methionine (Met). RESULTS: In the MMA group, the median levels of methylmalonic acid (259.10 (6.73 - 6429.28)), methylcitrate (4.39 (0 - 248.96)), C3 (8.52 (1.50 - 52.11) µmol/L) and C3/C2 (0.73(0.28 - 2.89)) were all higher than the upper limit values (0.2 - 3.6, 0 - 1.1, 0.50 - 4.00 µmol/L and 0.04 - 0.25 respectively). And they were all higher than those in the control group (0 (0 - 1.87), 0.10 (0 - 1.84), 1.40 (0.53 - 3.90) µmol/L, 0.10 (0.04 - 0.23), all P < 0.01). C3/C2 increased significantly in 15 patients while the C3 level remained normal. The median level of Met was normal in the isolate MMA group. But in patients with homocysteinemia, the level of 8.71 (0.68 - 31.95) µmol/L was below the reference value (10.00 - 35.00 µmol/L) and lower than that in the isolate MMA group (15.35 (4.18 - 59.50) µmol/L) and the control group (15.59 (10.20 - 34.68) µmol/L, all P < 0.05). CONCLUSIONS: Significant increases in the urine level of methylmalonic acid and C3/C2 may be specific to MMA. Organic acid analyses of gas chromatography-mass spectrometry and acylcarnitines with tandem mass spectrometry are required for a definite diagnosis of this disorder. And repeated tests and genomic mutation analysis are necessary for patients with mildly abnormal biochemical indices.

Variable phenotypes and outcomes associated with the MMACHC c.482G > A mutation: follow-up in a large CblC disease cohort.

BACKGROUND: The aim of this study was to characterize the variable phenotypes and outcomes associated with the methylmalonic aciduria and homocystinuria type C protein gene (MMACHC) c.482G > A mutation in 195 Chinese cases with CblC disease. METHODS: We carried out a national, retrospective multicenter study of 195 Chinese patients with CblC disease attributable to the MMACHC c.482G > A variant either in a homozygous or compound heterozygous state. The control group consisted of 200 patients diagnosed with CblC disease who did not possess the c.482G > A mutation. Clinical features, including disease onset, symptoms, biochemical metabolites, gene mutation, and follow-up outcomes were reviewed and analyzed in detail. The median follow-up period spanned 3 years and 8 months, with a range of 1 year and 2 months to 12 years and 10 months. RESULTS: Among 195 patients carrying the c.482G > A variant, 125 (64.1%) cases were diagnosed by newborn screening (NBS), 60 (30.8%) cases were detected due to disease onset, and 10 (5.1%) cases were identified from sibling diagnoses. One hundred and seventeen (93.6%) individuals who were diagnosed by NBS, and nine patients who came from sibling diagnoses remained asymptomatic in this study. From 69 symptomatic patients of the c.482G > A group, more patients presented with later onset, and the top six common clinical symptoms at disease onset were developmental delay (59.4%), lower limb weakness and poor exercise tolerance (50.7%), cognitive decline (37.7%), gait instability and abnormal posture (36.2%), seizures (26.1%), and psychiatric and behavioral disturbances (24.6%). In the 159 symptomatic patients lacking c.482G > A variants, the most frequently observed clinical manifestations at disease onset included developmental delay (81.8%), lethargy and feeding difficulty (62.9%), lower limb weakness and poor exercise tolerance (54.7%), prolonged neonatal jaundice (51.6%), vomiting (47.2%), and seizures (32.7%). Before treatment, the levels of blood propionylcarnitine, propionylcarnitine/acetylcarnitine ratio, and homocysteine in the c.482G > A group were significantly lower (P < 0.05) than those in the non-c.482G > A group, while the concentration of urinary methylmalonic acid was slightly lower (P > 0.05). The degree of decline in the above metabolites after treatment in different groups significantly differed in both plasma total homocysteine values and urinary methylmalonic acid levels (P < 0.05). In patients carrying the c.482G > A variant compared with the non-c.428G > A group, there were markedly lower rates of mortality (0.5% vs. 2.0%) and developmental delay (20.5% vs. 65.5%). When compared with individuals diagnosed due to disease onset, those identified through NBS in either group exhibited a reduced proportion of disease onset (6.7% vs. 100% in the c.482G > A group, 54.4% vs. 100% in the non-c.482G > A group), lower mortality (0.0% vs. 1.7% in the c.482G > A group, 0.0% vs. 3.6% in the non-c.482G > A group), and had a higher percentage of patients exhibiting normal psychomotor and language development (99.3% vs. 33.3% in the c.482G > A group, 58.9% vs. 10.9% in the non-c.482G > A group). CONCLUSIONS: The c.482G > A variant in MMACHC is associated with late-onset and milder phenotypes of CblC disease. Patients with this mutation tend to have a relatively better response to hydroxocobalamin, better metabolic control, and more favorable neurological outcomes. NBS and other appropriate pre-symptomatic treatments seem to be helpful in early diagnosis, resulting in favorable clinical outcomes. Video Abstract (MP4 136794 kb).

[Analysis of clinical data and genetic mutations in three Chinese patients with tyrosinemia type I].

OBJECTIVE: To analyze clinical data and gene mutations in 3 Chinese patients with tyrosinemia type I, and to explore the correlation between genotypes and phenotypes. METHODS: Three 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. RESULTS: Two 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. CONCLUSION: Tyrosinemia 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.

[Clinical study of oral alendronate in the treatment of pediatric osteogenesis imperfecta].

OBJECTIVE: To explore the clinical efficacy and safety of oral alendronate in children with osteogenesis imperfecta (OI). METHODS: Eleven OI children were recruited from August 2008 to April 2011 at Shanghai Institute of Pediatric Research to receive alendronate for a duration of (1.7 ± 0.3) years. The growth, fracture incidence, physical activity, the quality of daily life and safety parameters were evaluated. RESULTS: All patients obtained marked improvement. The rates of bone fractures decreased more remarkably than that at pre-treatment (0 - 1.2 fractures per year vs 0.5 - 5.0 fractures per year, medium 0 vs 1.40 fractures per year) (P = 0.003). Their levels of physical activities improved significantly (median level from 4 to 3, P = 0.004). There was significant post-treatment improvement in the self-care activity scores (median score from 43 to 73, P = 0.003). The bone density of lumbar vertebrae, long bones and metaphysis improved at post-treatment. The radiographic examinations revealed the thickness of bone cortex. The change in height did not show any significant difference. No change was found in the serum levels of calcium, phosphorus, parathyroid hormone, alkaline phosphate or other biochemical markers. No adverse reaction occurred throughout treatment. CONCLUSION: Oral alendronate treatment reduces the incidence of bone fracture and improves physical activity and life quality in OI children, and as a well-tolerated regimen, it is both safe and effective in clinical practice.

[Clinical characteristics and analysis of mass spectrometric data in 33 patients with maple syrup urine disease].

OBJECTIVE: To explore the clinical characteristics and the diagnostic method of maple syrup urine disease (MSUD). METHODS: From January 2003 to December 2011, a total of 14 000 patients with suspected inherited metabolism diseases were tested. The blood levels of leucine and valine of these patients were detected by tandem mass spectrometry. The urinary level of branched-chain α-ketoacids was tested by gas chromatography-mass spectrometry. And the diagnosis was based on the elevated levels of leucine and valine in blood and branched-chain α-ketoacids in urine. RESULTS: Thirty-three MSUD patients were confirmed. Their median age of initial visit was 0.17 years old (range: 7 days to 30 years old). The peak onset age of them was 2-30 days old, including 28 cases of neonatal onset (84.8%). The presenting symptoms of 28 cases were feeding difficulties (n=14), poor response, lethargy and seizures. Their median blood levels of leucine and valine (1901 (458-5804) and 600 (315-1617) µmol/L) were significantly higher than their normal levels ((50-300) and (60-250) µmol/L, both P<0.01). Their urinary levels of 2-OH-isovaleric acid, 2-keto-isovaleric acid, 2-keto-3-methylvaleric acid, 2-keto-isocaproic and acetylglycine (262.5 (5.4-624.3), 35.8 (1.9-156.0), 133.8 (7.4-611.5), 518.7 (17.2-2121.2) and 280.5 (11.0-1087.9) respectively) significantly higher than their normal levels (0, <0.1, 0, 0, <0.1 respectively, all P<0.01). In 5 intermittent MSUD patients, their blood levels of leucine and valine (402 (348-958) and 556 (322-808) µmol/L) were significantly higher than their normal levels (both P<0.01). The urinary level of 2-OH-isovaleric acid was significantly higher than its normal levels (P<0.01) while the urinary levels of other α-ketoacids were normal. CONCLUSIONS: The confirmation of MSUD remains difficult because of a lack of specific clinical features. The detections of tandem mass spectrometry and gas chromatography-mass spectrometry may aid its early diagnosis.

[Prenatal diagnosis of mucopolysaccharidosis type II].

OBJECTIVE: To establish a method of iduronate-2-sulfatase (IDS) activity assay and mutation analysis of IDS gene for the prenatal diagnosis of mucopolysaccharidosis type II (MPSII). METHODS: Prenatal diagnosis of two cases was performed using cultured fetal amniotic fluid cells. Enzyme activity of IDS in cultured fetal amniotic fluid cells extracted from the two pregnant women at high risk of MPS II was measured. Meanwhile, genomic DNA was extracted for fetal gender testing and mutation analysis of the IDS gene. RESULTS: Enzyme activity assay showed that IDS activity in amniotic fluid cells was significantly decreased. IDS gene sequencing showed that the male fetus was hemizygous mutant, and the female fetus was carrier of heterozygous mutation. Therefore the male fetus was an MPS II patient and the female fetus was a mutation carrier. CONCLUSION: Determination of IDS activity in fetal amniotic fluid cells together with IDS gene mutation analysis is a rapid, sensitive and accurate method of prenatal diagnosis of MPS II. Using this method, prenatal diagnosis for pregnant women at high risk of MPSII can be achieved.

[Application of enzyme assay and gene analysis in the prenatal diagnosis for a family with glycogen storage disease type II].

OBJECTIVE: To carry out prenatal diagnosis for a glycogen storage disease type II (GSD II ) affected family. METHODS: The acid-α -glucosidase (GAA) activity was measured in whole leukocytes and cultured amniocytes with 4-methylumbelliferyl-α -D-glucopyranoside as substrate and with acarbose as inhibitor. The coding regions of GAA gene were amplified by polymerase chain reaction and analyzed by direct DNA sequencing. RESULTS: The proband and the fetus had low GAA activity (12.3% and 1.1% of the average normal range, respectively). Mutation analysis of the GAA gene revealed a novel nonsense mutation p.W738X and a reported nonsense mutation p.E888X in both the proband and the fetus; the reported pseudodeficiency allele c.[1726G to A: 2065G to A] was found in the proband, the mother and the fetus. CONCLUSION: The proband and the fetus were both GSD II affected. A combination of GAA activity analysis and mutation analysis is efficient for the prenatal diagnosis of GSD II. Mutation analysis should be a routine method in the prenatal diagnosis of GSD II in Asian population, where pseudodeficiency allele can cause low GAA activity in normal individuals which is relatively common in Asian.

[Studies on the clinical manifestation and SLC25A13 gene mutation of Chinese patients with neonatal intrahepatic cholestasis caused by citrin deficiency].

OBJECTIVE: To investigate the clinical and laboratory features of neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD) and to characterize the molecular basis and prognosis of this disease. METHODS: Twenty-six patients with NICCD were collected because of idiopathic intrahepatic cholestasis and jaundice. The diagnosis was made by routine laboratory data collection, tandem mass spectrometry (MS-MS) and gas chromatography mass spectrometry (GC-MS) analyses. SLC25A13 gene mutation was analyzed by using polymerase chain reaction (PCR), direct DNA sequencing and restriction fragment length polymorphism analyses. The patients were followed up for nearly 2 years. RESULTS: The NICCD patients showed low birth weight and the average onset of jaundice was 29 days. Laboratory data showed liver dysfunction, hyperbilirubinemia, hypoproteinemia, high levels of alpha-fetoprotein, prolonged prothrombin time, hypoglycemia and hyperammonemia. MS-MS analysis of the blood samples revealed specific elevation of citrulline, methionine, threonine, tyrosine and elevation of free carnitine, short-chain and long-chain acylcarnitines. GC-MS analysis of the urine samples showed elevated 4-hydroxyl phenyllactic acid and 4-hydroxyl phenylpyruvic acid. Twelve different mutations were identified, including 4 novel mutations, i.e., G386V, R467X, K453R and 1192-1193delT. Forty-four mutated alleles were identified in the 52 alleles (84.6% ). Among them, 851del4, 1638ins23 and IVS6+5G>A mutations were the most frequent mutations, accounting for 40.9%, 20.5% and 11.4% of the total alleles examined respectively. Five of the 26 patients have not been recovered, including 4 died and 1 accepted liver transplantation. No obvious relationship was found between the genotype and phenotype in NICCD. CONCLUSION: The 851del4, 1638ins23 and IVS6+5G>A mutations are the hot-spot mutations in Chinese NICCD patients. Some NICCD patients have poor prognosis.

[Mutational analysis of patients with 6-pyruvoyltetrahydrobiopterin synthesis deficiency].

OBJECTIVE: To determine the gene mutation spectrum of patients with 6-pyruvoyltetrahydrobiopterin synthesis deficiency (PTPSD) in Mainland China. METHODS: The 6-pyruvoyltetrahydrobiopterin synthesis gene lz(PTS)lz was analyzed in 55 PTPSD patients by using PCR-restriction fragment length polymorphism (PCR-RFLP) and direct DNA sequencing. The relationship between the genotype and phenotype was analyzed. RESULTS: Eighteen mutations were identified and the detection rate of gene mutation was 95.28%. Four hot-spot mutations, namely P87S (40.57%), N52S(13.21%), D96N(12.26%) and IVS1nt-291A to G(10.38%) were found in this study, and the first three were associated with severe phenotype. The P87L was reported firstly in Chinese patients, and the Q13X, M80T, IVS4nt-2A to G, L93M and K131N were novel mutations. CONCLUSION: The P87S, N52S, D96N and IVS1nt-291A to G mutations are the hot-spots mutations of the PTS gene in Chinese PTPSD patients. Using PCR-RFLP technique to screen the mutations in the PTS gene can increase the efficiency of gene diagnosis.

[Gene mutation analyses in Chinese children with multiple carboxylase deficiency].

OBJECTIVE: To confirm the diagnosis of multiple carboxylase deficiency (MCD) on the gene level and explore the mutations in Chinese children with MCD. METHODS: Biotinidase (BT) and holocarboxylase synthetase (HLCS) genes were analyzed by PCR and direct sequencing for the 4 BT deficiency patients and 8 HLCS deficiency patients, respectively. The identified mutations in the parents of the patients and 50 normal controls were screened by PCR-restriction fragment length polymorphism and direct DNA sequencing. RESULTS: Total detection rate of gene mutation is 100% in the 12 children with MCD. Six mutations were detected in the 4 children with BT deficiency, they were c. 98-104del7ins3, c. 1369G>A (V457M), c. 1157G>A(W386X), c. 1284C>A(Y428X), c. 1384delA and c. 1493_1494insT. The last four were novel mutations. Four mutations were found in the 8 children with HLCS deficiency. They were c. 126G>T (E42D), c. 1994G>C (R665P), c. 1088T>A (V363D) and c. 1522C>T (R508W). The last two were hot-spot mutations [75%(12/16)], and c. 1994G>C (R665P) was a novel mutation. CONCLUSION: This study confirmed the diagnosis of 12 patients with MCD on the gene level. Six mutations were found in the BT gene and 4 in the HLCS gene, including 5 novel mutations. Two mutations of the HLCS gene are probably hot-spot mutations in Chinese children with HLCS deficiency.

[The investigation of differential diagnostic development and incidence of tetrahydrobiopterin deficiency].

OBJECTIVE: To investigate the development of differential diagnosis of tetrahydrobiopterin (BH4) deficiency among patients with hyperphenylalaninemia (HPA) in provinces or cities of China and to investigate the incidence of BH4 deficiency. METHODS: Of the thirteen hundreds and ninety-two patients with HPA received, the differential diagnosis for BH4 deficiency during 1993 - 2007 were enrolled in this study. Of which, 591 patients came from outpatient and 801 patients' samples from other provinces or cities were sent to author's laboratory to investigate the case number of differential diagnosis for BH4 deficiency in provinces or cities of China according to the data from both outpatient case histories and laboratory as to investigating the development of differential diagnosis in the whole country. To discuss the diagnostic criteria for BH4 deficiency was according to the results of urinary pterin analysis, determination of dihydropteridine reductase (DHPR) activity and the tetrahydrobiopterin loading test as well as to get the incidence of BH4 deficiency and find some provinces or cities with higher incidence of BH4 deficiency in China. RESULTS: (1) The number of HPA patients, who were performed by urinary pterin analysis and the determination of DHPR activity, were remarkably increased in last three years (2005 - 2007). The patient numbers of both urinary pterin analysis and DHPR activity determination were 217 and 198 respectively in 2005. And in 2007 they increased to 511 and 458, which was about 2.3 times than that in 2005. The patients came from 29 provinces or cities in 2007. (2) The urinary biopterin and biopterin percent were key marks for diagnosis of 6-pyruvoyl tetrahydropterin synthase (PTPS) deficiency. The less than 5% [(1.41 +/- 1.10)%] biopterin percent and very low biopterin level [(0.14 +/- 0.17) mmol/mol Cr] were found in 96.83% (61/63) patients with PTPS deficiency in this study. The blood phenylalanine level was remarkably decreased to normal range at 2 - 6 hours after BH4 loading test. The very low DHPR activity was a final diagnostic mark for DHPR deficiency. The very low DHPR activities of 0.27 nmol/(min x 5 mm disc) (6.11% - 7.00% of normal controls) were found in two patients with DHPR deficiency in this study. (3) The incidences of PTPS deficiency and DHPR deficiency among 1392 patients with hyperphenylalaninemia were 8.41% (117/1392) and 0.18% (2/1108) respectively. About 67.23% (80/119) patients with BH4 deficiency came from the south of Yangtze liver. The 80% (8/10) provinces or cities with higher incidence of BH4 deficiency are located in eastern and southern China. The incidence of PTPS deficiency among patients with HPA and normal newborns was 10.81% (8/74) and 0.007 per thousand (8/1,121,429) respectively in Shanghai, China according to data from neonatal screening. CONCLUSION: The awareness of differential diagnosis for BH4 deficiency from clinic pediatricians has been increased in most provinces or cities of China in last three years, but it should be more strengthened.

[Diagnosis, treatment and gene mutation analysis in children with holocarboxylase synthetas deficiency].

OBJECTIVE: To report the clinical diagnosis, treatment and follow-up of children with holocarboxylase synthetas(HCS) deficiency and explore the gene mutation spectrum of the disease. METHODS: Eleven children with HCS deficiency were enrolled. Mass spectrometry analysis and biotinidase activity determination were used for diagnosis of HCS deficiency. HCS gene mutations were analyzed by PCR directed sequencing methods. Ten patients received oral biotin treatment (10-40 mg/d). Clinical effects of biotin treatment were observed. RESULTS: All 11 cases developed apathetic, lethargy and metabolic acidosis at different degrees, and 10 cases presented with skin lesions. The average blood 3-hydroxyisovaleryl-carnitine concentrations and urinary 3-methylcrontonylglycine and methylcitrate concentrations increased significantly. The biotinidase activity increased, being higher over 30% of the normal reference value. Four mutations in HCS gene were identified, and they were c.1522C>T (R508W), c.1088T>A (V363D), c.126G>T (E42D) and c.1994G>C (R665P) (a new variant) and the frequency was 50%, 29%, 7% and 14% respectively. The symptoms disappeared in 10 cases 1-2 weeks after biotin treatment, and blood and urinary abnormal metabolites were gradually reduced to normal 2-6 months after treatment. CONCLUSIONS: HCS deficiency is characterized by nervous system damage, skin lesions and metabolic acidosis. Mass spectrometry analysis, biotinidase activity determination and gene mutation analysis may be helpful in the definite diagnosis of this disorder. The effect of early biotin treatment is satisfactory. The mutations R508W and V363D might be hot-spots in Chinese children with HCS deficiency.

Application of isoxanthopterin as a new pterin marker in the differential diagnosis of hyperphenylalaninemia.

BACKGROUND: This study aimed to explore the value of applying a new pterin marker (isoxanthopterin) to the traditional urine pterin analysis to reduce the rate of mis-diagnosis of 6-pyruvoyltetrahydropterin synthase deficiency (PTPSD) and improve the accuracy of diagnosis. METHODS: We compared the urine neopterin (N), biopterin (B), isoxanthopterin (Iso), B% and Iso% levels between patients with phenylalanine hydroxylase deficiency and those with PTPSD, and found the most specific pterin biomarkers by ROC analysis. A positive cut-off value of urine pterins was determined. The effect of combined Iso% + B + B% in reducing PTPSD mis-diagnosis was evaluated, and the different urine pterin levels in PTPSD and false PTPSD (FPTPSD) were compared. The concordance of PTPSD diagnosis by the new pterin scheme and gene mutation analysis was determined. RESULTS: (1) Urinary B, B%, Iso and Iso% were significantly lower in PTPSD than those in phenylalanine hydroxylase-deficiency group (P < 0.01); (2) Iso%, B%, and B were the most specific markers; (3) The positive cut-off values of B, B%, Iso% for PTPSD were < 0.17 mmoL/moLCr, < 5.0%, and < 9.5%, respectively; (4) urinary B + B% + Iso% scheme significantly reduced the false-positive rate of PTPSD compared to traditional ones. The Iso% levels in FPTPSD group were higher than the ones in PTPSD group; (5) an accuracy of diagnosis for PTPSD was increased by 9-19% when Iso% was introduced to urinary pterin scheme. CONCLUSIONS: Iso% is helpful to reduce the rate of misdiagnosis of PTPSD in the diagnosis by urinary pterin analysis for hyperphenylalaninemias and improve the accuracy of diagnosis. This approach is worthy of further development and increased utilization.