Inborn errors of metabolism detectable by tandem mass spectrometry in Beijing.

Background Individual inborn errors of metabolism (IEMs) are rare disorders. Expanded newborn screening for IEMs by tandem mass spectrometry (TMS) is an efficient approach for early diagnosis. Here we provide the newborn screening program for the application of this approach (between July 2014 and March 2019) to the identification of newborns in Beijing at risk of developing a potentially fatal disease. Methods The amino acids and acylcarnitines in dried blood spots were analyzed by TMS. Diagnoses of newborns with elevated metabolites were confirmed by gas chromatography-mass spectrometry, biochemical studies, and genetic analysis. Results Among the healthy newborns, 16 metabolic disorder cases were confirmed, giving a total birth prevalence of 1:3666 live births. Organic acidemia (OA) was the most common (9/16 patients; 56%), and methylmalonic acidemia was the most frequently observed OA (7/9 patients; 89%). Five infants were diagnosed with methylmalonic acidemia with homocystinuria type CblC, two with isolated methylmalonic acidemia, one with propionic acidemia, and one with isovaleric acidemia. Four patients (4/16, 25%) were diagnosed with hyperphenylalaninemia. One suffered with medium-chain acyl CoA dehydrogenase deficiency, one with carnitine uptake deficiency, and one with citrin deficiency. Eleven cases underwent genetic analysis. Seventeen mutations in eight IEM-associated genes were identified in 11 confirmed cases. Symptoms were already present within 2 days after birth in 44% (7/16) cases. The infant with propionic acidemia died at 7 days after birth. The other cases received timely diagnosis and treatment, and most of them grew well. Conclusions The results illustrate challenges encountered in disease management highlighting the importance of newborn screening for inherited metabolic disorders, which is not yet nationally available in our country. Regional newborn screening programs will provide a better estimation of the incidence of IEM.

A pilot study on newborn screening for congenital adrenal hyperplasia in Beijing.

Background A provisionary screening programme for 21-hydroxylase deficiency (21-OHD) was initiated in Beijing in 2014. The aim of this study was to investigate the incidence and the associated clinical characteristics of neonatal congenital adrenal hyperplasia (CAH) in Beijing and to provide evidence-based guidance for its application in CAH screening. Methods Live birth newborns (n=44,360) were screened for CAH in Beijing from July 2014 to April 2018. The levels of 17-hydroxyprogesterone (17-OHP) in the blood were estimated using the time-resolved fluoroimmunoassay. Neonates with a positive result and a level >30 nmol/L of 17-OHP were called for a retest. CAH was diagnosed based on further laboratory findings combined with clinical signs, such as weight loss, feeding difficulties, skin pigmentation, and atypical genitalia. Through a review of medical records, the clinical findings including molecular data were reported. Results Of the 44,360 neonates screened, 280 cases were deemed positive. Of these, 203 neonates were recalled for further tests and six patients (three boys and three girls) were diagnosed with CAH. Five cases of classic salt-wasting and one case of simple virilising 21-OHD were identified. The incidence of CAH in Beijing was 1:7393. The most frequent 21-OHD mutation was c.293-13C/A>G. Conclusions The incidence of CAH in Beijing was higher than the national average. The results support the need for neonatal CAH screening in Beijing. This pilot study demonstrates the clinical characteristics of 21-OHD through newborn screening. Early detection and treatment through neonatal screening may reduce mortality rates and optimise developmental outcomes.

Whole-exome sequencing as a powerful tool for identifying genetic causes in a patient with POLG-related disorders and phenylketonuria.

OBJECTIVE: This study's aim was to identify the genetic causes in a patient with phenylketonuria and hearing loss, liver disease, developmental and mental retardation, hypotonia, and external ophthalmoplegia. METHODS: Whole-exome sequencing and Sanger sequencing analysis were used to determine the genetic causes of manifestations in a young boy with hearing loss, liver disease, develop-mental and mental retardation, hypotonia, and external ophthalmoplegia. RESULTS: We found that the child harbored polymerase gamma ( POLG) compound heterozygous mutations, c.2617G>A (p.E873K) and c.3550G>A (p.D1184N), and phenylalanine hydroxylase ( PAH) compound heterozygous mutations, c.721C>T (p.R241C) and c.728G>A (p.R243Q). Among them, the POLG p.E873K mutation is a novel mutation and is not present in the Exome Aggregation Consortium database, Genome Aggregation database, and 1000 Genomes database. The two heterozygous mutations were each inherited from both of the child's parents. This finding suggested that the phenotype and the genotype were segregated. CONCLUSION: Using whole-exome sequencing, we not only identified PAH mutations causing phenylketonuria, but also identified the genetic cause of the mitochondrial disease and found a novel POLG mutation. Our findings could be useful in helping future parents obtain healthy embryos through assisted reproductive technology.

[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.