Steroid profile in dried blood spots by liquid chromatography tandem mass spectrometry: Application to newborn screening for congenital adrenal hyperplasia in China

BACKGROUND

Newborn screening for congenital adrenal hyperplasia (CAH) using 17-hydroxyprogesterone dissociation-enhanced, lanthanide fluorescence immunoassay (DELFIA) generates a large number of false-positive results. The present study aimed to improve the sensitivity of the CAH neonatal screening by including second-tier steroid profiling in dried blood spots (DBS) using liquid chromatography tandem mass spectrometry (LC-MS/MS).

METHODS

We developed and validated a LC-MS/MS method for simultaneous determination of six steroids in DBS, including androstenedione, testosterone, 17-hydroxyprogesterone, 11-deoxycortisol, 21-deoxycortisol, and cortisol. Two 5-mm blood spots were eluted by internal standard working solution. We analyzed 1170 DBS samples from neonates to determine gestational age-specific reference intervals. In order to test the specificity of the second-tier method, we analyzed 707 cards with a positive screening by DELFIA.

RESULTS

Values of intra- and inter-day precision coefficients of variance and accuracy were 2.0%-13.3% and 85.8%-114.5%, respectively. Recovery ranged from 85.0% to 106.9%. The lower limit of quantification was 0.5 ng/mL for 21-deoxycortisol, 0.25 ng/mL for 17-hydroxyprogesterone and cortisol, and 0.1 ng/mL for testosterone, androstenedione, and 11-deoxycortisol. In addition, the linearity range was 0.25-50 ng/mL (R² > 0.99). According to the 17-hydroxyprogesterone levels and ratios of (androstenedione + 17-hydroxyprogesterone)/cortisol in the 707 positive screening samples, 77 neonates should receive recall visit. The number of false-positive results reduced by 89.1%. Totally, 18 newborns were diagnosed with 21-hydroxylase deficiency, one with P450 oxidoreductase deficiency and one with 11β-hydroxylase deficiency. With two-tier screening, the positive predictive value increased to 26.0%.

CONCLUSIONS

The second-tier steroid profiling by LC-MS/MS reduced the false-positive rate and improved the positive predictive value of CAH screening. We suggest applying this steroid profiling assay as a second-tier test for CAH screening in China.

Resource utilization of medical waste under COVID-19: Waste mask used as crude oil fluidity improver

The disposal of medical waste has become an increasing environmental issue since the COVID-19 epidemic outbreaks. Conventional disposal methods have produced waste of fossil resources and environmental problems. In this study, the waste medical mask-derived materials were tested as viscosity reducer and pour point depressant to evaluate the possibility of being used as crude oil fluidity improver. The results show that the materials derived from the three parts of the waste medical mask can reduce the viscosity and pour point of each crude oil samples from different oilfields in China. The middle layer of the medical mask (PP-2) displays the highest efficiency, and the viscosity reduction rate and maximum pour point reduction reaches 81% and 8.3 °C at 500 ppm, respectively. A probable mechanism of improving rheological properties of the crude oil samples by the medical mask-derived materials was further proposed after the differential scanning calorimetry (DSC) analysis and the wax crystal morphology analysis. We hope this work could provide a way to solve the current environmental issues under COVID-19.

Prenatal Diagnosis of Isovaleric Acidemia From Amniotic Fluid Using Genetic and Biochemical Approaches

Background: Isovaleric acidemia (IVA) is an inborn error of leucine metabolism and different approaches have been applied to its prenatal diagnosis. However, systemic application of a biochemical strategy is rare. To evaluate its reliability and validity, we conducted a retrospective study of our experience with metabolite measurement together with genetic analysis in IVA prenatal diagnosis at a single center.

Methods: A total of eight pregnancies whose probands were diagnosed as IVA were referred to our center for prenatal diagnosis. Prenatal data of genetic analysis and metabolite measurement using tandem mass spectrometry (MS/MS) and gas chromatography/mass spectrometry (GC/MS) in amniotic fluid (AF) samples were retrospectively reviewed.

Results: Genetic and biochemical results were both available in these eight at-risk fetuses. Among them, two fetuses had higher levels of isovalerylcarnitine (C5) and C5/acetylcarnitine (C2) in AF compared with normal reference range and, thus, were determined to be affected, both of whom were found to carry compound heterogeneous mutations according to genetic analysis. The remaining six fetuses were determined to be unaffected based on a normal AF metabolite profile, except one showed slightly elevated C5 and they were found to be carriers according to genetic analysis. However, the level of isovalerylglycine (IVG) could not be detected at all in both groups.

Conclusion: The biochemical analysis, as a quick and convenient method, could be an additional reliable option for the prenatal diagnosis of IVA, especially in families with inconclusive genetic results, and can achieve a more precise diagnosis in conjunction with mutation analysis.

[Disease spectrum analysis of children with inherited metabolic diseases detected by gas chromatography-mass spectrometry of urinary organic acids]

Objective: To investigate the spectrum of amino acid, organic acid, and fatty acid oxidative metabolic diseases in children diagnosed by detecting urinary organic acid levels using gas chromatography-mass spectrometry. Methods: From January 2005 to December 2021, clinical data of 2 461 children diagnosed with inherited metabolic diseases (IMD) by gas chromatography-mass spectrometry, in combination with tandem mass spectrometry and genetic testing in Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine were retrospectively analyzed. Results: Among 2 461 children, 1 446 were male and 1 051 were female. A total of 32 types of IMD were detected among 2 461 patients, which included 10 amino acid disorders in 662 cases (26.9%), 6 common diseases were hyperphenylalaninemia, citrin deficiency, ornithine carbamoyltransferase deficiency, maple syrup urine disease, alkaptonuria, and tyrosinemia-I, 17 types of organic acidemias in 1 683 cases (68.4%), 6 common diseases were methylmalonic acidemia, propionic acidemia, valeric acidemia-type Ⅰ, isovaleric acidemia, 3-methylcrotonyl-CoA carboxylase deficiency and multiple carboxylase deficiency and 5 fatty acid β oxidative defects in 116 cases (4.7%), 2 common diseases were multiple acyl-CoA dehydrogenase deficiency and short-chain acyl-CoA dehydrogenase deficiency). Conclusion: Among the diseases diagnosed by analyzing urinary organic acid profiling with gas chromatography-mass spectrometry, the most common are organic acidemias, followed by amino acid disorders and fatty acid oxidation defects.

Investigation of GALNS variants and genotype-phenotype correlations in a large cohort of patients with mucopolysaccharidosis type IVA

Mucopolysaccharidosis type IVA (MPS IVA) is a rare autosomal recessive disorder resulting from the deficiency of N-acetylgalactosamine-6-sulfate sulfatase (GALNS) caused by pathogenic variants in the GALNS gene. A systematic analysis for genotype-phenotype correlation is essential due to hundreds of variants generating different levels of residual GALNS activity and causing a wide degree of clinical manifestation effects. Here, we retrospectively analyzed clinical and genetic data of 108 unrelated patients with MPS IVA to investigate the variants spectrum of GALNS and assess their clinical effects. In this cohort, 82 patients were classified as severe, 14 as intermediate, and 12 as mild. One hundred and one GALNS variants were identified, of which 47 were novel. Most patients with at least one GALNS null variant were classified as severe phenotype (92%, 33/36). Missense variants mapped to different residues of GALNS protein resulted in different phenotypes in patients with MPS IVA. Ninety-two percent of patients with two missense variants mapped to buried residues were classified as severe (92%, 24/26), while at least one missense variant mapped to surface residues was identified in patients with biallelic missense variants presenting intermediate MPS IVA (78%, 7/9) and presenting mild MPS IVA (86%, 6/7). Our study contributes to a better understanding of the molecular spectrum of GALNS variants and their clinical implications. Based on the data herein reported, we generated a systematic flowchart correlating the GALNS variants to assist in phenotype prediction and classification of patients with MPS IVA.

The Follow-Up of Chinese Patients in cblC Type Methylmalonic Acidemia Identified Through Expanded Newborn Screening

Objective: The cblC type of combined methylmalonic acidemia and homocystinuria, an inherited disorder with variable phenotypes, is included in newborn screening (NBS) programs at multiple newborn screening centers in China. The present study aimed to investigate the long-term clinical benefits of screening individual.

Methods: A national, retrospective multi-center study of infants with confirmed cblC defect identified by NBS between 2004 and 2020 was conducted. We collected a large cohort of 538 patients and investigated their clinical data in detail, including disease onset, biochemical metabolites, and gene variation, and explored different factors on the prognosis.

Results: The long-term outcomes of all patients were evaluated, representing 44.6% for poor outcomes. In our comparison of patients with already occurring clinical signs before treatment to asymptomatic ones, the incidence of intellectual impairment, movement disorders, ocular complications, hydrocephalus, and death were significantly different (p < 0.01). The presence of disease onset [Odd ratio (OR) 12.39, 95% CI 5.15–29.81; p = 0.000], variants of c.609G>A (OR 2.55, 95% CI 1.49–4.35; p = 0.001), and c.567dupT (OR 2.28, 95% CI 1.03–5.05; p = 0.042) were independently associated with poor outcomes, especially for neurodevelopmental deterioration.

Conclusion: NBS, avoiding major disease-related events and allowing an earlier treatment initiation, appeared to have protective effects on the prognosis of infants with cblC defect.

Diagnosis and follow-up of Glycogen Storage Disease (GSD) Type VI from the largest GSD center in China

Glycogen storage disease (GSD) type VI is a glycogenolysis disorder caused by variants of PYGL. Knowledge about this disease is limited because only approximately 50 cases have been reported. we investigated the clinical profiles, molecular diagnosis, and treatment outcomes in patients with gsd VI from 2000 to 2021. The main initial clinical features of this cohort include hepatomegaly, short stature, elevated liver transaminases, hypertriglyceridemia, fasting hypoglycemia, and hyperuricemia. After uncooked cornstarch treatment, the stature and biochemical parameters improved significantly (P < 0.05). However, hyperuricemia recurred in most patients during adolescence. Among the 56 GSD VI patients, 54 biallelic variants and two single allelic variants of PYGL were identified, of which 43 were novel. There were two hotspot variants, c.1621-258_2178-23del and c.2467C>T p.(Gln823*), mainly in patients from Southwest and South China. c.1621-258_2178-23del is a 3.6 kb deletion that results in an out-of-frame deletion r.1621_2177del and an in-frame deletion r.1621_2265del. Our data show for the first time that long-term monitoring of uric acid is recommended for older GSD VI patients. This study also broadens the variant spectrum of PYGL and indicates that there are two hot-spot variants in China. This article is protected by copyright. All rights reserved.

Clinical, genetic profile and therapy evaluation of 55 children and 5 adults with sitosterolemia

BACKGROUND

Sitosterolemia is a rare autosomal recessive disease characterized by phytosterol accumulation in the blood and tissues. However, the detailed clinical and genetic spectra are lacking.

OBJECTIVE

To describe and compare the clinical, biochemical, genetic, therapeutic, and follow-up characteristics of 55 pediatric and five adult sitosterolemia patients.

METHODS

Clinical, genetic and therapeutic data from 60 patients at Xinhua Hospital from January 2016 to June 2021 were retrospectively collected.

RESULTS

Pediatric patients' manifestations included xanthomas(93%), hematological disorders(30%), arthralgia(24%), splenomegaly(11%), atherosclerosis(10%). Adult patients had symptoms such as atherosclerosis(5/5), xanthomas(4/5), hematological disorders(3/5), arthralgia(3/5), splenomegaly(3/5). Elevated total cholesterol(TC) and low-density lipoprotein cholesterol(LDL-C) were observed in 96% patients (pediatric 98%, adult 3/4), and phytosterol levels in 100% patients. The age of onset was also negatively correlated with blood TC (P < 0.0001, r = -0.5548) and LDL-C (P = 0.0001, r = -0.4859) levels. Targeted treatments resulted in symptomatic remission(pediatric 96%, adult 4/5), and significantly decreased lipid and phytosterol levels(all P<0.05). In the dietary-therapy cohort(n=34), blood lipid levels decreased(all P<0.05). In the 13 pediatric patients from the dietary-therapy cohort who switched from dietary to combination therapy with ezetimibe, dietary therapy decreased TC and LDL-C levels by 54% and 52%, and ezetimibe further decreased them by 18% and 20%, respectively. Further, we identified 15 novel ABCG5/ABCG8 variants.

CONCLUSIONS

This study expands the clinical and genetic spectra of sitosterolemia. The low-phytosterol diet is the cornerstone of sitosterolemia treatment. Ezetimibe can further decrease blood lipid levels and increase daily dietary phytosterol tolerance.

Gene expression profiles in the brain of phenylketonuria mouse model reversed by the low phenylalanine diet therapy

To gain insight into the potential protective mechanisms of low phenylalanine diet (LPD) in phenylketonuria (PKU), gene expression profiles were studied in the cerebral cortex and hippocampus of a PKU mouse model (BTBR-Pah^enu2). PKU mice were fed with low Phe diet (LPD-PKU group) and normal diet (PKU group). Wild-type mice were treated with normal diet (WT group) as control. After 12 weeks, we detected gene expression in the cerebral cortex and hippocampus of the three groups by RNA-sequencing, and then screened the differentially-expressed genes (DEGs) among the groups by bioinformatics analyses. We found that the transcriptional profiles of both cerebral cortex and hippocampus changed markedly between PKU and WT mice. Furthermore, LPD changed the transcriptional profiles of the cerebral cortex and the hippocampus of PKU mice significantly, especially in the cerebral cortex, with overlaps of genes that changed with the disease and altered by LPD treatment. In the cerebral cortex, hundreds of DEGs enriched in a wide spectrum of biological processes, molecular function, and cellular component, including nervous system development, axon development and guidance, calcium ion binding, modulation of chemical synaptic transmission, and regulation of protein kinase activity. In the hippocampus, the overlapping genes were enriched in positive regulation of long term synaptic, negative regulation of excitatory postsynaptic potential, positive regulation of synapse assembly. Our results showed that genes impaired in PKU and then rescued by LPD might indicate the potential protective capability of LPD in the PKU brain.

An intronic variant disrupts mRNA splicing and causes FGFR3-related skeletal dysplasia

OBJECTIVES

Achondroplasia and hypochondroplasia are the most common forms of disproportionate short stature, of which the vast majority of cases can be attributed to the hotspot missense mutations in the gene FGFR3. Here we presented cases with a novel cryptic splicing variant of FGFR3 gene and aimed to interrogate the variant pathogenicity.

CASE PRESENTAITON

In whole exome sequencing of two patients with hypochondroplasia-like features, a de novo intronic variant c.1075 + 95C>G was identified, predicted to alter mRNA splicing. Minigene assay showed that this intronic variant caused retention of a 90-nucleotide segment of intron 8 in mRNA, resulting in a 30-amino acid insertion at the extracellular domain of the protein. This is the first likely pathogenic splicing variant identified in the FGFR3 gene and was detected in one additional patient among 26 genetically unresolved patients.

CONCLUSTIONS

Our results strongly suggest that c.1075 + 95C>G is a recurrent mutation and should be included in genetic testing of FGFR3 especially for those patients with equivocal clinical findings and no exonic mutations identified.

Different mutations in the MMUT gene are associated with the effect of vitamin B12 in a cohort of 266 Chinese patients with mut-type methylmalonic acidemia: A retrospective study

BACKGROUND

To summarize the relationship between different MMUT gene mutations and the response to vitamin B12 in MMA.

METHODS

This was a retrospective study of patients diagnosed with mut-type MMA. All patients with mut-type MMA were tested for responsiveness to vitamin B12.

RESULTS

There were 81, 27, and 158 patients in the completely responsive, partially responsive, and nonresponsive groups, respectively, and the proportions of symptom occurrence were 30/81 (37.0%), 21/27 (77.8%), and 131/158 (82.9%), respectively (p < .001). The median levels of posttreatment propionyl carnitine (C3), C3/acetyl carnitine (C2) ratio in the blood, and methylmalonic acid in the urine were all lower than pretreatment, and the median level of C3/C2 ratio in the completely responsive group was within the normal range. In 266 patients, 144 different mutations in the MMUT gene were identified. Patients with the mutations of c.1663G>A, c.2080C>T, c.1880A>G, c.1208G>A, etc. were completely responsive and with the mutations of c.1741C>T, c.1630_1631GG>TA, c.599T>C, etc. were partially responsive. The proportions of healthy/developmental delay outcomes in the three groups were 63.0%/23.5%, 33.3%/40.7%, and 13.3%/60.1%, respectively (p < .001).

CONCLUSION

Different mutations in the MMUT gene are associated with the effect of vitamin B12 treatment.

Clinical features and outcomes of patients with cblC type methylmalonic acidemia carrying gene c.609G>A mutation

To explore the clinical features and long-term outcomes of patients with cblC type methylmalonic acidemia (MMA) carrying c.609G>A (p.W203X) mutation of gene. The clinical and laboratory findings of 720 patients with MMA carrying the c.609G>A mutation were retrospectively analyzed. There were 172 cases carrying homozygous mutations of c.609G>A (group A), 169 cases carrying compound heterozygous mutations of c.609G>A with c.482G>A (p.R161Q), c.80A>G or c.394C>T (p.R132X) (group B), and 379 cases carrying compound heterozygous mutations of c.609G>A with c.658_660delAAG(p.K220del), c.315A>Tor c.567dupT(p.I190fs13)(group C).The clinical manifestations, the level of blood acylcarnitine, homocysteine and urinary organic acid, and the therapeutic efficacy were compared among groups. Logistic regression was used to analyze the factors influencing the prognosis of patients. There were 306 patients (42.5%) detected from newborn screening, including 156 cases with disease onset; and 414 patients were not detected from the screening, among whom 10 cases were diagnosed by testing after the sibling confirmed, and the remaining 404 were clinical cases. In 560 patients with disease onset, the median onset age is (3 days to 20 years). The onset age of patients in group B was later than that in group A and group C (<0.01). Patients aged mostly manifested as vomiting, diarrhea, feeding difficulties and convulsions, while those year mostly manifested as movement disorders and mental retardation. Patients with renal disease all carried mutations of c.80A>G or c.482G>A, and patients with pulmonary hypertension all carried c.80A>G mutations. A total of 621 cases had long-term follow-up, 156 cases (25.1%) developed well, 433 cases (69.7%) had development delay and 32 cases (5.2%) died. The available data of 559 cases were analyzed by logistic regression, and the results showed that the neonatal screening, disease onset, age of onset and gene mutation site were significantly associated with the prognosis of patients (<0.05 or <0.01). The c.609G>A mutation in gene is associated with early-onset MMA, and most patients, clinical onset occurred within 1 month after birth. The neonatal screening and early treatment can improve the prognosis of patients,whereas clinical onset is unfavorable for prognosis. Patients with c.609G>A homozygous mutation have a worse prognosis than those with the compound heterozygous mutation of c.609G>A with other mutations.

[Analysis of six children with 3-methylglutaconic aciduria]

Objective: To explore the clinical characteristics, genotypes and long-term outcomes of individuals with 3-methylglutaconic aciduria. Methods: The clinical features, biochemical data, genetic test results and treatment outcomes of six children with 3-methylglutaconic aciduria admitted to the Department of Endocrinology, Genetics and Metabolism, Xinhua Hospital from February 2017 to February 2019 were retrospectively analyzed and the Gesell developmental diagnosis schedule was performed to evaluate the development of four patients. Results: Among 6 children with 3-methylglutaconic aciduria 2 were males and 4 were females.Four cases had 3-methylglutaconic aciduria type Ⅰ and 2 cases had 3-methylglutaconic aciduria with deafness,encephalopathy, and Leigh-like syndrome. Five of 6 patients were detected by newborn screening among whom 4 remained asymptomatic, and only one had a postmortem diagnosis. Among them, 4 patients remained asymptomatic, while two presented with clinical symptoms such as jaundice and dyspnea and the age of disease onset was 1 and 2 days respectively. The concentration of 3-methylglutaconic acid in urine of all affected individuals was between 22.38 and 77.09 mmol/molCr, which was above the normal value. Genetic tests were performed for all patients. Eleven variants were identified in 2 genes, of which 10 variants were novel and only c.442C>T p.(R148X) has been previously reported; Seven variants (c.656-2delA, EX5-EX6 Del, c.942+3A>G, c.373C>T p.(R125W), c.895-3C>G, c.667C>T p.(R223X) and c.894+5G>A) were in AUH gene. The others (c.548G>A p.(R138Q), c.442C>T p.(R148X), c.1339C>T p.(R447X) and c.973dupA p.(M325Nfs*5) were in SERAC1 gene. After being treated with leucine diet restriction and L-carnitine, 4 patients with AUH gene variation who were from asymptomatic phase developed normally, whereas those 2 patients with SERAC1 gene variation had a poor prognosis. During the follow-up, 2 patients exhibited varying degrees of psychomotor retardation, the rest had normal course of development. Conclusions: There are significant clinical heterogeneities among individuals with 3-methylglutaconic aciduria. The most common pathogenic variants are splicing variations, followed by nonsense, missense and frameshift mutations. Leucine-free diet and oral L-carnitine therapy are effective for some patients. Newborn screening is essential for early diagnosis and improvement of prognosis.

One-year follow-up of thyroid function in 23 infants with Prader- Willi syndrome at a single center in China

Endocrine disorders are common in patients with Prader-Willi syndrome (PWS). Whether hypothyroidism is present in patients with PWS, and especially infants and young children, remains unclear. The aims of this study were to evaluate thyroid function in patients with PWS, to assess the prevalence of thyroid dysfunction, and to evaluate the effect of growth hormone on thyroid function. Subjects were 23 patients with PWS ages 3 months to 3 years who were followed for up to one year. Four patients were lost to follow-up after the first visit. The remaining 19 patients were treated with recombinant human growth hormone (rhGH). PWS was diagnosed based on a genetic analysis. Free thyroxine (FT4), free triiodothyronine (FT3), and thyroid-stimulating hormone (TSH) levels were evaluated before and after growth hormone treatment. A total of 9 patients (9/23 = 39.1%) developed abnormal thyroid function. Five out of 23 patients (21.7%) had abnormal thyroid function before growth hormone treatment. Four patients developed thyroid dysfunction during the 3- to 9-month period of rhGH treatment. Of the 9 patients with abnormal thyroid function, 7 (5 boys, 2 girls) had central hypothyroidism, and the other 2 patients had subclinical hypothyroidism. TSH levels were higher in patients with PWS due to maternal uniparental disomy (UPD) than in patients with PWS due to a 15q11-q13 deletion. The prevalence of hypothyroidism was high in infants and young children with PWS. Thyroid function should be regularly monitored in patients with PWS at both diagnosis and follow-up.

Evaluation of the Clinical, Biochemical, Neurological, and Genetic Presentations of Glutaric Aciduria Type 1 in Patients From China

Purpose

To characterize the phenotypic and genotypic variations associated with Glutaric aciduria type 1 (GA1) in Chinese patients.

Methods

We analyzed the clinical, neuroradiological, biochemical, and genetic information from 101 GA1 patients in mainland China.

Results

20 patients were diagnosed by newborn screening and the remaining 81 cases were identified following clinical intervention. Macrocephaly was the most common presentation, followed by movement disorders and seizures. A total of 59 patients were evaluated by brain MRI and 58 patients presented with abnormalities, with widening of the sylvian fissures being the most common symptom. The concentration of glutarylcarnitine in the blood, glutarylcarnitine/capryloylcarnitine ratio, and urine levels of glutaric acid were increased in GA1 patients and were shown to decrease following intervention. A total of 88 patient samples were available for genotyping and 74 variants within the GCDH gene, including 23 novel variants, were identified. The most common variant was c.1244-2A > C (18.4%) and there were no significant differences in the biochemical or clinical phenotypes described for patients with the four most common variants: c.1244-2A > C, c.1064G > A, c.533G > A, and c.1147C > T. Patients identified by newborn screening had better outcomes than clinical patients.

Conclusion

Our findings expand the spectrum of phenotypes and genotypes for GA1 in Chinese populations and suggest that an expanded newborn screening program using tandem mass spectrometry may facilitate the early diagnosis and treatment of this disease, improving clinical outcomes for patients in China.

Rapid detection of twenty-nine common Chinese glucose-6-phosphate dehydrogenase variants using a matrix-assisted laser desorption/ionization-time of flight mass spectrometry assay on dried blood spots

BACKGROUND

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common inherited disease. Current neonatal screening methods for G6PD deficiency primarily rely on the use of biochemical tests. However, only 15%-20% of female carriers were estimated to have been detected using these tests. As a better alternative, DNA-based tests could be used for G6PD deficiency screening. We aimed to develop a matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) assay for G6PD variant detection.

METHODS

A MALDI-TOF MS assay with multiprimer extension (multi-PEX) was developed to rapidly and accurately detect the 29 common G6PD variants in the Chinese population using a dried blood spot as a template. A parallel study screening 571 unrelated neonatal samples using the MALDI-TOF MS and fluorescence quantitative enzymatic assays was performed. All results were confirmed by Sanger sequencing in a blind study.

RESULTS

In 571 unrelated neonatal samples, 34 positive samples, including 26 samples from hemizygous males and eight samples from heterozygous females, were correctly identified, yielding a clinical sensitivity of 100%. The results were validated using Sanger sequencing with 100% concordance. In contrast, the fluorescence quantitative enzymatic assay had a 75% false negative and 88.8% false positive rate for the detection of heterozygous G6PD deficient females.

CONCLUSIONS

We established a reliable MALDI-TOF MS assay for G6PD deficiency screening in the Chinese population maximizing the chance of detection of heterozygous G6PD deficient females and reducing the false negative and false positive rates associated with routinely used newborn screening procedures.

[Clinical features and gene mutations of 6 patients with carnitine palmitoyltransferase 1A deficiency]

The clinical and biochemical data and gene sequencing results of patients with carnitine palmitoyltransferase 1A deficiency were analyzed, in order to improve the understanding of the disease. Six patients (5 males and 1 female, aged from 1 to 8 years old) with carnitine palmitoyltransferase 1A deficiency from Department of Pediatric Endocrinology and Genetic Metabolism, Xinhua Hospital between 2008 and 2019 were included. Two cases were detected by neonatal screening and had no clinical symptoms. The remaining 4 cases all showed seizures induced by fever, vomiting or diarrhea. All the 6 patients showed increased serum free carnitine (C0), decreased hexadecanoylcarnitine (C16) and octadecanoylcarnitine (C18), and increased C0/(C16+C18). Meanwhile, compound heterozygous mutations of CPT1A gene were detected in all 6 patients, of which 2 were reported mutations (c.281+1G>A and c.968-8C>T), and 10 were new mutations. The new mutations included 6 missense mutations, 1 nonsense mutation, 1 deletion mutation and 2 splicing mutations. Detection of free carnitine and acyl carnitine by tandem mass spectrometry is helpful for early screening and diagnosis of carnitine palmitoyltransferase 1A deficiency.

Clinical, Biochemical, and Molecular Analyses of Medium-Chain Acyl-CoA Dehydrogenase Deficiency in Chinese Patients

Objective

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is a rare inherited metabolic disorder of fatty acid β-oxidation. The present study aimed to evaluate clinical and biochemical manifestations, and the mutation spectrum of this disorder in a large cohort of Chinese patients.

Methods

A total of 24 patients were enrolled, and blood acylcarnitine and urinary organic acid levels were measured by tandem mass spectrometry and gas chromatography–mass spectrometry (GC–MS), respectively. Mutations in the ACADM gene were detected by Sanger or next-generation sequencing. Clinical progression, acylcarnitine spectra, and mutations were analyzed and described in detail.

Results

Among the 24 patients, six cases were diagnosed because of disease onset with symptoms such as vomiting, diarrhea, convulsion, and hypoglycemia; 18 patients without symptoms were diagnosed by newborn screening (NBS). All patients who accepted treatment after diagnosis developed normal intelligence and physique. The concentrations of octanoylcarnitine, the octanoylcarnitine/decanoylcarnitine ratio, and the octanoylcarnitine/acetylcarnitine ratio in the blood and urinary dicarboxylic acid concentrations were consistently elevated. Blood biomarkers failed to decrease after treatment. DNA sequencing revealed seven known and 17 novel mutations in the ACADM gene of patients. Mutation p.T150Rfs^∗4 was most frequent, followed by p.R31C, p.F103Y, p.I223T, p.G362E, and c.387+1delG.

Conclusion

Despite biochemical abnormalities, medium-chain acyl-CoA dehydrogenase deficiency showed relatively mild clinical phenotypes with low mortality and optimistic prognoses in China. NBS is crucial for early diagnosis, treatment, and prognosis.

Clinical, biochemical, and genotype-phenotype correlations of 118 patients with Niemann-Pick disease Types A/B

Niemann-Pick disease Types A and B (NPA/B) are autosomal recessive disorders caused by variants in the sphingomyelin phosphodiesterase-1 (SMPD1) gene. This study aimed to describe and characterize a cohort of 118 patients diagnosed with NPA/B based on clinical, biochemical, and molecular findings, and to identify sound correlations between laboratory findings and clinical presentations. Decreased peripheral leukocyte acid sphingomyelinase activity levels and increased plasma 7-ketocholesterol levels were significantly correlated with disease onset and severity of the clinical course. We identified 92 different sequence SMPD1 variants, including 41 novel variants, in 118 NPA/B patients (19 NPA, 24 intermediate type, 75 NPB). The most prevalent mutation was p.Arg602His, which accounted for 9.3% of the alleles. Patients homozygous for p.Arg602His or p.Asn522Ser showed a late-onset form of the NPB phenotype. The homozygous SMPD1 variant p.Tyr500His correlated with the early-onset NPB clinical form. Additionally, homozygous variants p.His284SerfsX18, p.Phe465Ser, and p.Ser486Arg were associated with the neuronopathic NPA clinical form. The homozygous variant p.Arg3AlafsX74 was associated with the intermediate clinical form. Our study contributes to the understanding of the natural history of NPA/B and assists in the development of efficacious treatments for patients afflicted with this devastating lysosomal storage disorder.

Value of amniotic fluid homocysteine assay in prenatal diagnosis of combined methylmalonic acidemia and homocystinuria, cobalamin C type

BACKGROUND

Combined methylmalonic acidemia and homocystinuria, cobalamin C type (cblC defect) is the most common inborn error of cobalamin metabolism, and different approaches have been applied to its prenatal diagnosis. To evaluate the reliability of biochemical method for the prenatal diagnosis of cblC defect, we conducted a retrospective study of our 10-year experience at a single center.

METHODS

248 pregnancies whose probands were diagnosed as cblC defect were referred to our center for prenatal diagnosis from January 2010 to December 2019. Prenatal data of Hcy levels determined by enzymatic cycling assay, acylcarnitine analysis using liquid chromatography tandem mass spectrometry, organic acid analysis using gas chromatography mass spectrometry, and genetic analysis by direct sequencing of 248 at-risk fetuses were retrospectively reviewed.

RESULTS

For 2.0 and 16.0 μmol/L levels of Hcy AF samples, the relative errors were - 2.5% and 2.8%, respectively. The respective measurement uncertainties were 13.07% and 14.20%. For the 248 at-risk fetuses, 63 fetuses were affected and 185 fetuses were unaffected. Hcy level of 13.20 (6.62-43.30) μmol/L in 63 affected fetuses was significantly higher than that in 185 unaffected fetuses of 2.70 (0.00-5.80) μmol/L, and there was no overlap between the affected and unaffected groups. The diagnostic sensitivity and specificity of Hcy were 100% and 92.05%, respectively. The positive and negative predictive values of the combination of Hcy, propionylcarnitine (C3), ratio of C3 to acetylcarnitine (C2; C3/C2), methylmalonic acid (MMA), and methylcitric acid (MCA) were both 100%. Sixteen fetuses displayed inconclusive genetic results of MMACHC variants, in which seven fetuses were determined to be affected with elevated levels of Hcy, C3, C3/C2 and MMA, and their levels were 18.50 (6.70-43.30) μmol/L, 8.53(5.02-11.91) μmol/L, 0.77 (0.52-0.97), 8.96 (6.55-40.32) mmol/mol Cr, respectively. The remaining nine fetuses were considered unaffected based on a normal amniotic fluid metabolite profile.

CONCLUSIONS

Hcy appears to be another characteristic biomarker for the prenatal diagnosis of cblC defect. The combination of Hcy assay with acylcarnitine and organic acid analysis is a fast, sensitive, and reliable prenatal diagnostic biochemical approach. This approach could overcome the challenge of the lack of genetic analysis for families with at-risk cblC defect fetuses.

Chromosomal microarray analysis in fetuses with high-risk prenatal indications: A retrospective study in China

OBJECTIVE

The present study aimed to determine the diagnostic value of prenatal chromosomal microarray analysis (CMA) for fetuses with several indications of being at high risk for various conditions.

MATERIALS AND METHODS

This retrospective analysis included 1256 pregnancies that were prenatally evaluated due to high-risk indications using invasive CMA. The indications for invasive prenatal diagnosis mainly included ultrasound anomalies, high-risk for maternal serum screening (MSS), high-risk for non-invasive prenatal tests (NIPT), family history of genetic disorders or birth defects, and advanced maternal age (AMA). The rate of clinically significant genomic imbalances between the different groups was compared.

RESULTS

The overall prenatal diagnostic yield was 98 (7.8%) of 1256 pregnancies. Clinically significant genomic aberrations were identified in 2 (1.5%) of 132 patients with non-structural ultrasound anomalies, 36 (12.7%) of 283 with structural ultrasound anomalies, 2 (4.5%) of 44 at high-risk for MSS, 38 (26.6%) of 143 at high-risk for NIPT, 11 (3.8%) of 288 with a family history, and 7 (2.1%) of 328 with AMA. Submicroscopic findings were identified in 29 fetuses, 19 of whom showed structural ultrasound anomalies.

CONCLUSION

The diagnostic yields of CMA for pregnancies with different indications greatly varied. CMA could serve as a first-tier test for structural anomalies, especially multiple anomalies, craniofacial dysplasia, urinary defects, and cardiac dysplasia. Our results have important implications for genetic counseling.

Conformational Stability of Poly (N-Isopropylacrylamide) Anchored on the Surface of Gold Nanoparticles

To verify the temperature sensitive failure of poly (N-isopropylacrylamide) (PNIPAM) anchored on the surface of gold nanoparticles (AuNPs), the UV-Vis spectra with temperature variations of the following aqueous solutions respectively containing AuNPs-PNIPAM, Au-PNIPAM/PNIPAM, PNIPAM, in different media (including salt, ethanol, HCl and cetyltrimethylammoniumbromide (CTAB)), were systematically determined. The results indicated that the UV-Vis spectrum of AuNPs-PNIPAM suspension hardly changed even above the Lower Critical Solution Temperature (LCST) of PNIPAM, but that of Au-PNIPAM/PNIPAM sharply increased only in absorbance intensity. A possible mechanism of the failed temperature sensitivity of PNIPAM anchored on the surface of AuNPs was proposed. Being different from free PNIPAM molecules, a strong interaction exists among PNIPAM molecules anchored on the surface of AuNPs, restraining the change in conformation of PNIPAM. The temperature sensitivity of Au-PNIPAM/PNIPAM originates from the free PNIPAM molecules rather than the anchored PNIPAM one. The changing electrostatic interaction could effectively regulate the aggregation behavior of AuNPs-PNIPAM and enhance its sensitivity to temperature.

A rare mutation c.1663G > A (p.A555T) in the MMUT gene associated with mild clinical and biochemical phenotypes of methylmalonic acidemia in 30 Chinese patients

Background

Methylmalonic acidemia is an inherited organic acid metabolic disease. It involves multiple physiological systems and has variable manifestations. The primary causative gene MMUT carries wide range of mutations, and one of them, c.1663G > A (p.A555T), is considered to be a rare type, which is seen more frequently in Asian than other populations. So far, little is known about the clinical features of patients carrying this mutation. In the present study, we aimed to define the clinical and biochemical features of the patients with this genotype.

Methods

Among 328 mut type methylmalonic acidemia patients from multiple hospitals in China, we collected 30 compound heterozygous patients sharing the mutation c.1663G > A (p.A555T) in the MMUT gene. Their clinical characteristics and biochemical index were described in detail and compared with methylmalonic acidemia patients without this variant.

Results

Most of these patients were diagnosed via newborn screening (26/30), treated in a timely manner, and kept healthy (24/30). Disease onset occurred in 7 patients. Developmental delay or intellectual impairment occurred in 4 patients. 100% of these patients (29/29) were responsive to Vitamin B12 administration. The blood propionylcarnitine, blood propionylcarnitine/acetylcarnitine ratio, urinary methylmalonic acid, urinary methylcitric acid before and after treatment in c.1663G > A (p.A555T) carrying patients were much lower than those in non-c.1663G > A (p.A555T) carrying patients.

Conclusion

Compared to patients with other mutations in the MMUT gene, patients with the c.1663G > A (p.A555T) mutation showed later onset, milder clinical phenotype, lighter biochemical abnormalities, better vitamin B12 responsiveness, lower morbidity, easier metabolic control, and thereby better prognosis. Newborn screening project plays an important role in early diagnosis, treatment, and prognosis of these patients.

Clinical and molecular characteristics of 69 Chinese patients with ornithine transcarbamylase deficiency

Background

This study aimed to describe the clinical and biochemical features of Chinese patients with ornithine transcarbamylase deficiency (OTCD), and to investigate the mutation spectrum of OTC gene and their potential correlation with phenotype.

Methods

Sixty-nine patients with OTCD were enrolled between 2004 and 2019. Clinical and laboratory data were reviewed retrospectively from medical records.

Results

Fifteen cases (13 males, 2 females) presented with early onset; 53 cases (21 males, 32 females) had late onset, and one female was asymptomatic. The median onset age was 1.5 years (range 1 day–56 years). Urine orotic acid levels were increased in all patients tested, while only 47.6% of patients showed decreased serum levels of citrulline. The peak plasma ammonia levels were higher in early-onset patients than in late-onset patients (P < 0.01). Fifty-four different mutations of OTC gene were identified and 18 of them were novel. R277W (10.6%) was the most common mutation, followed by G195R (4.6%) and A209V (3.0%). By June 2019, 41 patients had survived, 24 were deceased, and 4 were lost to follow-up. Among the survivors, 13 patients had received liver transplantation at a median age of 3 years, with a one-year survival rate of 100%. The mortality of OTCD is extremely high among patients with early onset (80.0% versus 24.5% in patients with late onset).

Conclusions

The evaluation of serum citrulline level is of limited value in diagnosis of OTCD, while urine orotic acid detection and genetic testing are more helpful.

High Detection Rate of Copy Number Variations Using Capture Sequencing Data: A Retrospective Study

BACKGROUND

Capture sequencing (CS) is widely applied to detect small genetic variations such as single nucleotide variants or indels. Algorithms based on depth comparison are becoming available for detecting copy number variation (CNV) from CS data. However, a systematic evaluation with a large sample size has not been conducted to evaluate the efficacy of CS-based CNV detection in clinical diagnosis.

METHODS

We retrospectively studied 3010 samples referred to our diagnostic laboratory for CS testing. We used 68 chromosomal microarray analysis-positive samples (true set [TS]) and 1520 reference samples to build a robust CS-CNV pipeline. The pipeline was used to detect candidate clinically relevant CNVs in 1422 undiagnosed samples (undiagnosed set [UDS]). The candidate CNVs were confirmed by an alternative method.

RESULTS

The CS-CNV pipeline detected 78 of 79 clinically relevant CNVs in TS samples, with analytical sensitivity of 98.7% and positive predictive value of 49.4%. Candidate clinically relevant CNVs were identified in 106 UDS samples. CNVs were confirmed in 96 patients (90.6%). The diagnostic yield was 6.8%. The molecular etiology includes aneuploid (n = 7), microdeletion/microduplication syndrome (n = 40), and Mendelian disorders (n = 49).

CONCLUSIONS

These findings demonstrate the high yield of CS-based CNV. With further improvement of our CS-CNV pipeline, the method may have clinical utility for simultaneous evaluation of CNVs and small variations in samples referred for pre- or postnatal analysis.