Pseudodeficiency alleles affect the newborn screening of glycogen storage disease typeⅡ / 中华检验医学杂志

Objective@#To investigate the effect of pseudodeficiency alleles on the newborn screening of glycogen storage disease type Ⅱ(GSDⅡ) by using afluorometric enzymatic assay to determine acid α-glucosidase (GAA) activity in dried blood spot (DBS).@*Methods@#A total of 30 507 newborns′ DBSs, obtained from Newborn Screening Center of Xinhua Hospital Shanghai Jiao Tong University School of Medicine from May to December 2017, were screened for GSD Ⅱ by fluorometric enzymatic assay of GAA activity. The suspected positive DBSs after the first and second screening were directly analyzed by Sanger sequencing of GAA to confirm the diagnosis. Retrospective analysis of 3 172 controls without GSDⅡand 36 GSD Ⅱ patients were conducted to investigate the carrier status of pseudodeficiency alleles. Statistical analysis of frequency of pseudodeficiency alleles were carried out by Chi-square test or Fisher exact probability test.@*Results@#GAA activity of 30 507 newborns showed a positively skewed distribution.Twenty-nine cases of newborns, suspected to be GSDⅡwere confirmed to be normal with genetic analysis of the original DBSs. Among the 29 suspected positive cases, 24 cases were homozygous for pseudodeficiency alleles c.[1726A/A; 2065A/A], and the other 5 cases were c.[1726G/A; 2065G/A] heterozygote. The frequency of c.1726G>Ahomozygote in 3 172 non-GSD Ⅱcontrols was 2.08% (66/3 172), and c.1726G>A homozygote occurred in allelic conjunction with c.2065G>Ahomozygote. Frequency of c.[1726A; 2065A] haplotype in 3 172 controls was 3.2%(206/6 344). Frequency of c.[1726A/A; 2065A/A] homozygote in 36 GSDⅡpatients (16.67%, 6/36) was significantly higher than that in non-GSD Ⅱcontrols(2.08%, 66/3 172) (χ2=34.517, P<0.001).@*Conclusions@#Pseudodeficiency alleles show a high frequency in Chinese, which leads to a high false positive rate in the newborns screening of GSDⅡ.The afterword genetic analysis of the original DBS after the GAA activity screening could reduce the effect of pseudodeficiency alleles on the newborns screening of GSDⅡ.

Pseudodeficiency alleles affect the newborn screening of glycogen storage disease typeⅡ / 中华检验医学杂志

Objective To investigate the effect of pseudodeficiency alleles on the newborn screening of glycogen storage disease typeⅡ(GSDⅡ) by using afluorometric enzymatic assay to determine acidα-glucosidase (GAA) activity in dried blood spot (DBS). Methods A total of 30507 newborns' DBSs, obtained from Newborn Screening Center of Xinhua Hospital Shanghai Jiao Tong University School of Medicine from May to December 2017, were screened for GSDⅡby fluorometric enzymatic assay of GAA activity. The suspected positive DBSs after the first and second screening were directly analyzed by Sanger sequencing of GAA to confirm the diagnosis. Retrospective analysis of 3172 controls without GSDⅡand 36 GSDⅡpatients were conducted to investigate the carrier status of pseudodeficiency alleles. Statistical analysis of frequency of pseudodeficiency alleles were carried out by Chi-square test or Fisher exact probability test. Results GAA activity of 30507 newborns showed a positively skewed distribution. Twenty-nine cases of newborns, suspected to be GSDⅡwere confirmed to be normal with genetic analysis of the original DBSs. Among the 29 suspected positive cases, 24 cases were homozygous for pseudodeficiency alleles c. [1726A/A; 2065A/A], and the other 5 cases were c. [1726G/A; 2065G/A] heterozygote. The frequency of c. 1726G>Ahomozygote in 3172 non-GSDⅡcontrols was 2.08％(66/3172), and c. 1726G>A homozygote occurred in allelic conjunction with c. 2065G>Ahomozygote. Frequency of c. [1726A; 2065A] haplotype in 3172 controls was 3.2％(206/6344). Frequency of c. [1726A/A;2065A/A] homozygote in 36 GSDⅡpatients (16.67％, 6/36) was significantly higher than that in non-GSDⅡcontrols(2.08％, 66/3172) (χ2=34.517, P<0.001). Conclusions Pseudodeficiency alleles show a high frequency in Chinese, which leads to a high false positive rate in the newborns screening of GSDⅡ.The afterword genetic analysis of the original DBS after the GAA activity screening could reduce the effect of pseudodeficiency alleles on the newborns screening of GSDⅡ.

The clinical and genetic analysis of glycogen storage disease type IV in 5 cases / 临床儿科杂志

Objective To investigate the characteristics of glycogen storage disease type IV (GSD IV) clinically, in laboratory tests and in gene mutation. Methods The clinical manifestations, biochemical indexes, activity of chitotriosidase, and the follow-up of the treatment in 5 cases of GSD IV were analyzed. Results Five patients (3 boys and 2 girls) aged 4 months - 5 years presented hepatosplenomegaly and elevated liver enzyme levels for 2 months at hospital visit. Two patients had motor developmental delay and weakness but their creatine kinase (CK) level were normal. Glycogen storage and liver fibrosis were observed in the liver biopsy in 4 patients. Target sequencing found that all 5 children carried the complex heterozygous mutation of the GBE1 gene with 2 reported mutations(p.R515C,p.R524Q)and 7 novel mutations.The novel mutation contains 5 missense mutations (p.I460T, p.F76S, p.F538V, p.L650R, p.W455R), one insertion mutations (c.141_142insGCGC), and one large fragment deletion (exon 3-7). Therefore, diagnosis of liver type of GSD IV was confirmed in those children. Two patients died of liver cirrhosis. The liver transplantation was performed due to liver cirrhosis in one patient whose chitotriosidase activity increased obviously before transplantation and decreased significantly after the transplantation and liver enzyme levels were returned to normal 4 months after transplantation. In the other two patients their growth and liver enzyme levels were normal;one had not received special treatments while the other was treated with raw corn starch and level of chitotriosidase was normal. Conclusions The clinical manifestations of GSD IV are heterogeneous. Target sequencing can be used for fast and noninvasive diagnosis of GSD IV. Chitotriosidase activity is useful in the prognosis assessment for GSD IV.

Prenatal diagnosis of methylmalonic acidemia using test of homocysteine and mass spectrometry in amniotic fluid / 中华检验医学杂志

Objective To explore the value of the combination of homocysteine analysis, liquid chromatography tandem mass spectrometry(LC-MS/MS)and gas chromatography mass spectrometry(GC/MS)in the prenatal diagnosis of combined methylmalonic acidemia and homocystinuria(cblC defect)in amniotic fluid.Methods This is a retrospective study of 187 cases of pregnancies that came to our hospital for prenatal diagnosis between 2014/01-2017/03,among which 78 cases′probands were cblC defect patients and 109 cases′probands were not organic academia patients(control group).Amniotic fluid samples from pregnant women were obtained at 16 -24 weeks of gestation.Propionylcarnitine(C3)and acetylcarnitine (C2)were measured by LC-MS/MS, methylmalonic acid and methylcitric acid were analyzed by GC /MS, and homocysteine was determined by fluorescence polarization immunoassay.Some pregnancies received MMACHC gene sequencing with cultured cells from amniotic fluid.Data were analyzed using Mann-Whitney U and Kruskal-Wallis H tests.Results Among those 78 pregnant women whose probands were diagnosed to be cblC defect,24 cases were diagnosed to be cblC defect(positive group)and 54 pregnant women were diagnosed to be negative(negative group).In positive group, levels of homocysteine, C3, C3/C2, methylmalonic acid and methylcitric acid were all significantly higher than their normal reference ranges, negative group and control group(P values are 0.00).Cases that were diagnosed to be cblC defect by MMACHC gene sequencing were all turned out to be positive in the tests of the above metabolites in amniotic fluid.Cases with negative results of the metabolites were all excluded to be cblC defect by gene sequencing. Besides,2 cases of pregnancies were diagnosed to be positive by homocysteine and mass spectrometric analysis while only one mutation were detected by gene sequencing.Conclusions The combination of homocysteine, LC-MS/MS and GC/MS analysis in amniotic fluid turns out to be reliable for prenatal diagnosis of cblC defect,which may further cover the defect of prenatal diagnosis of those pregnancies whose probands′gene mutation is unknown.

Molecular and prenatal diagnosis of a family with Fanconi anemia by next generation sequencing / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To provide prenatal diagnosis for a pregnant woman who had given birth to a child with Fanconi anemia with combined next-generation sequencing (NGS) and Sanger sequencing.</p><p><b>METHODS</b>For the affected child, potential mutations of the FANCA gene were analyzed with NGS. Suspected mutation was verified with Sanger sequencing. For prenatal diagnosis, genomic DNA was extracted from cultured fetal amniotic fluid cells and subjected to analysis of the same mutations.</p><p><b>RESULTS</b>A low-frequency frameshifting mutation c.989_995del7 (p.H330LfsX2, inherited from his father) and a truncating mutation c.3971C>T (p.P1324L, inherited from his mother) have been identified in the affected child and considered to be pathogenic. The two mutations were subsequently verified by Sanger sequencing. Upon prenatal diagnosis, the fetus was found to carry two mutations.</p><p><b>CONCLUSION</b>The combined next-generation sequencing and Sanger sequencing can reduce the time for diagnosis and identify subtypes of Fanconi anemia and the mutational sites, which has enabled reliable prenatal diagnosis of this disease.</p>

Prenatal diagnosis of methylmalonic acidemia by amniotic fluid metabolites analysis using mass spectrometry / 中华围产医学杂志

Objective To investigate the effect of tandem mass spectrometry and gas chromatography-mass spectrometry to make prenatal diagnosis of methylmalonic acidemia (MMA) by detecting organic acid and acylcarnitine in amniotic fluid.Methods From October 11,2007 to December 20,2014,131 pregnant women with MMA proband received prenatal diagnosis of MMA in Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (case group).Another 120 cases of pregnant women for conventional prenatal diagnosis at the same period were as control group.The pregnant women of two groups had the amniocentesis at 16 to 20 weeks of gestation.The levels of propionylcarnitine(C3) and acetylcarnitine(C2)in amniotic fluid were detected by tandem mass spectrometry.The methylmalonic acid and methylcitrate acid were detected by gas chromatography-mass spectrometry.MMA gene of cells in amniotic fluid of eighty fetuses with proband clearly diagnosed were detected by gene testing.Data were analyzed by Wilcoxon test.Results In case group,29 fetuses were found positive for higher level of C3,C3/C2,methylmalonic acid and methylcitrate acid compared with normal reference value,and the detected rate of fetal MMA was 22.1％(29/131).The levels of C3 and C3 / C2 in amniotic fluid of these 29 cases were higher than those in control group[8.13(2.42-16.70) vs 1.04(0.52-3.40) μmol/L,Z =-8.313; 0.77(0.30-1.79) vs 0.10(0.05-0.22),Z=-8.374; P ＜ 0.05 respectively].The levels of methylmalonic acid and methylcitrate acid were also higher[9.13(1.68-61.78) vs 0.00(0.00-1.31) mmol/mol Crea,Z=-11.348; 0.58(0.00-1.90) vs 0.05(0.00-0.52) mmol/mol Crea,Z=-6.632,P ＜ 0.05 respectively].For the other 102 cases in case group,the levels of C3,C3/C2,methylmalonic acid and methylcitrate acid were not higher than normal reference value,and were similar to those in control group (P ＞ 0.05); while they were lower than those of positive MMA fetuses (all P ＜ 0.05).Among 29 positive fetuses,16 fetuses were detected MMA gene,five were diagnosed as MUT forms of MMA and 11 were MMACHC forms of MMA.In 102 MMA negative fetuses,64 fetuses were detected MMA gene,44 were found one mutant site and 20 were found no gene mutation.The coincidence rate between gene detecting and mass spectrometry was 100％(80/80).Conclusions Mass spectrometry could be used to measure the C3,methylmalonic acid and methylcitrate acid levels in amniotic fluid of pregnant women with MMA proband to make prenatal diagnosis.

Gene mutations and prenatal diagnosis in families with maple syrup urine disease / 中华围产医学杂志

Objective Maple syrup urine disease (MSUD) is a rare metabolic disorder caused by deficiency of the activity of branched-chain 2-keto acid dehydrogenase complex.The complex contains E1α,E1β and E2 subunits which are encoded by BCKDHA,BCKDHB or DBT genes respectively.Mutation in any gene will cause MSUD.The aim of this study was to analyze the gene mutations of four cases with MSUD and carry out prenatal diagnosis for these four families for MSUD.Methods From 2005 to 2010,four neonates (two males and two females) were diagnosed as MSUD at 2,5,10and 26 days of life.The coding regions of BCKDHA gene and BCKDHB gene in the above four cases were amplified by polymerase chain reaction and analyzed by direct DNA sequencing.During the second pregnancy of the same mother,the amniotic fluid was drawn out at 16-20 weeks for gene mutation analysis after the amniocytes were cultured.Results Mutation analysis revealed six mutations in four patients,including four novel mutations (c.308T＞C,c.562G＞T,c.1279C＞G and c.1280-1291de112) and two previously reported mutations.Five mutations (c.308T＞C,c.562G ＞T,c.868G＞A,c.1279C＞G and c.1280-1291de112) were detected on BCKDHA gene in three patients.While one mutation (c.853C＞T) was found on BCKDHB gene in one patient.Only one mutation was found in the amniocytes of each patient's mother at their second pregnancies suggesting a MSUD heterozygous fetus.Conclusions Analysis of BCKDHA and BCKDHB allowed preliminary understand of gene mutations in the four MSUD families,and made prenatal diagnosis possible,which helped in consultation in the second pregnancy.