用判别式分析智力低下儿童及其母亲苯丙酮尿症杂合子的简易实验

作者提出了检测苯丙酮尿症(PKU)病人杂合子的分类系数和方程式。苯丙氨酸(Phe)、苯丙氨酸/酪氨酸(Tyr)、Phe~2/Tyr的几组变量组合可提供一个可靠的诊断,准确率达96%。作者随机选择病人进行计算,共分为两组:第一组选择判别式函数,第二组核对方法是否适当。用此方法对26名非特异性智力低下儿童及他们的母亲进行PKU杂合子的检测,发现PKU致病基因携带者的比率很高,用这种方法将两对母子、四个儿童、五个母亲归类为杂合子。对受试者准确分类的概率高于90%。本实验是在半禁食情况下进行PKU杂合子多元判别分析的。用不同群体样本:一组     

天津地区已婚群体苯丙酮尿症杂合子筛查

目的　寻找一种筛查苯丙酮尿症(phenylketonuria,PKU)杂合子的可靠易行方法。方法　用反相高效液相色谱快速检测血浆苯丙氨酸和酪氨酸实验方法,对101余例已知PKU杂合子和2023名已婚群体分别进行检测和统计分析。结果　已知PKU杂合子的Phe浓度、Phe/Tyr和Phe     

β-珠蛋白生成障碍性贫血基因分析

本文分析了宜昌地区3个家系8例β-珠蛋白基因突变类型，发现以IVS-2-654(C→T)占多数6/8，次为41-42(-4bp)2／8．3例先证者分别为41-42(-4bp)／IVS-2-654(C→T)双重杂合子；IVS-2-654(C→T)纯合子；IVS-2-654(C→T)杂合子．β-珠蛋白生成障碍性贫血治疗困难，脾切除对于双重杂合子及纯合子患者疗效差于杂合子患者，目前进行产前诊断能达优生目的．     

一例Pah基因杂合缺失合并半合子突变病例分析

目的 对一例苯丙氨酸羟化酶(PAH)缺乏症患儿进行基因组测序,分析其Pah基因变异情况,以明确病因。方法 采用免疫荧光法对新生儿进行血苯丙氨酸(Phe)浓度检测,血Phe浓度>2.0mg/dL进行尿蝶呤谱分析以鉴别病因;进一步用基因测序技术对其静脉血进行Pah基因测序,测序数据与正常人基因组进行比对,分析基因变异情况。结果 该患儿血Phe浓度为46.88 mg/dL(2765.92μmol/L),正常新生儿Phe浓度<2.0mg/dL,苯丙氨酸/酪氨酸(Phe/Tyr)为49.65(参考范围0.1～1.5),尿蝶呤谱结果为52.08(正常新生儿：19.8～50.3);基因测序结果发现1个缺失突变和1个剪接突变,分别为：exon6杂合缺失和第6外显子c.611A>G剪接突变,其中exon6片段缺失在人类基因突变数据库(HGMD)中未报道;患儿根据治疗前最高血Phe进行分类为经典型PAH缺乏症,需低Phe饮食治疗,并定期监测血Phe浓度水平。结论 初步明确了该患儿的病因为杂合缺失合并半合子突变,Pah基因型为exon6杂合缺失/c.611A>G;并发现了1种未报道基...     

用PCR方法进行复合型地中海贫血产前诊断

本文介绍用聚合酶链反应和特异性寡核苷酸探针斑点杂交方法对6种不同形式的复合型地中海贫血高危胎儿12例进行产前诊断，结果是正常胎儿3例．β地贫杂合子3例，HbE杂合子1例，α地贫1复合HbE杂合子1例，α地贫1复合β地贫1例，重型α地贫(Hb—Batrs’水肿胎儿)2例，重型α地贫1例。     

儿童运动及智能障碍者四氢生物蝶呤代谢病筛查及基因研究

目的探讨四氢生物蝶呤（tetrahydrobiopterin，BH4）代谢中各酶缺乏在儿童运动及智能发育障碍者中发生率及基因突变。方法对100例运动及智能障碍患者进行苯丙氨酸（phenylalanine，Phe）及BH4负荷试验、尿蝶呤谱分析、红细胞二氢蝶啶还原酶测定，并对部分患者进行多巴治疗性诊断；对诊断为多巴反应性肌张力障碍（dopa-responsive dystonia，DRD）及6-丙酮酰四氢蝶呤合成酶（6-pyruvoyl tetrahydropterin synthase，PTS）缺乏者做基因突变检测。结果100例中70例基础血Phe浓度正常，6例（6％）诊断为DRD；30例有高苯丙氨酸血症[Phe（1022±290）μmol／L]，8例（8％）诊断为VIS缺乏症，22例（22％）诊断为苯丙氨酸羟化酶缺乏症。发现2例DRD患者其三磷酸鸟苷环化酶基因（GTP cyclohydrolase 1 gene，GCHI）突变为IVS5＋3insT，8例FIS缺乏症患者存在PTS基因7种突变类型，其中259C→T，286G→A，155A→G最常见，占75％。结论一些肌张力障碍或智能障碍者是由于BH4代谢障碍所致，有必要做筛查诊断以明确诊断。     

应用全基因组扩增技术对β-地中海贫血进行胚胎植入前遗传学诊断

目的 探讨对β-地中海贫血进行胚胎植入前遗传学诊断的方法。方法 夫妇双方分别为β41-42(-TCTT)及IVS-I 654(C→T)突变杂合子，在本中心进行体外受精-胚胎移植和胚胎植入前遗传学诊断。结果 13个胚胎中共有11个胚胎经PCR分析后获得明确诊断，正常胚胎2个(18．1％)；杂合子胚胎6个(54．5％)；双重杂合子胚胎3个(27．3％)。共移植3个胚胎，其中2个正常胚胎、1个杂合子胚胎。在胚胎移植后5周B超示三胎妊娠，孕8周自然减一胎，并于孕20周时经产前诊断，证实均为健康胎儿。现已分娩双胎分别为正常和杂合子。结论 成功应用全基因组扩增技术对β-地中海贫血进行胚胎植入前遗传学诊断，并分娩健康双胎。     

β-地中海贫血产前基因诊断的临床应用研究

目的 探讨多重等位基因特异PCR基因诊断β－地中海贫血的临床应用价值。方法 选择四川人群中的5种突变热点（CD41－42，CD17，nt-28,nt-29,IVS-Ⅱ 654），对29个家系中的β－地中海贫血贫血患儿及其家庭成员进行了检测，共89例，其中羊水产前诊断6例。结果 异常染色单体数99条，其中未知突变15条，可诊断率84．7％。产前基因诊断中11例为单个突变的杂合子，4例双重杂合子，1例胎儿基因型为CD17／N或CD17／U。结论 多重等位基因特异PCR可用于四川地区临床β－地中海贫血高风险胎儿的产前基因诊断。     

应用串联质谱技术进行新生儿高苯丙氨酸血症79205例筛查结果分析

目的探讨串联质谱技术在怀化市新生儿高苯丙氨酸血症(HPA)筛查中的应用价值,了解怀化市新生儿高苯丙氨酸血症的检出率。方法选择出生72h后经充分哺乳的新生儿,采集足跟血,制成干血滤纸片,应用串联质谱技术(MS/MS)测定血苯丙氨酸(Phe)、酪氨酸(Tyr)浓度及其比值(Phe/Tyr)进行HPA筛查,筛查原标本血Phe浓度120μmo L/L,或同时伴有Phe/Tyr2.0为阳性,初筛阳性者立即召回复查,复查阳性者应用气相色谱-质谱进行尿有机酸分析及下一代测序技术(NGS)检测阳性患儿的突变基因。结果怀化市2015年3月-2017年12月共筛查新生儿79 205例,其中男性42 592例,女性36 613例,确诊HPA患儿6例,HPA检出率为1/13 201。结论应用串联质谱技术进行新生儿HPA筛查的检出率为1/13 201,明显高于之前报道的应用茚三酮荧光法进行新生儿HPA筛查的检出率1/40 758。应用串联质谱技术进行新生儿HPA筛查是一种准确、可靠的方法。     

广西桂林地区β-地中海贫血基因突变类型的探讨

目的了解桂林地区β-地中海贫血（以下简称13地贫）的基因型构成情况及分布，为制定本地区β-地贫防治计划提供参考，有效控制重型地中海贫血患儿出生。方法应用双重PCR结合反应斑点杂交技术对桂林地区426例经筛查至少符合HbA2增高、HbF增高、出现HbE带三项之-的样本进行17种中国人常见的β-地贫基因突变检测。结果在受检的426例样本中共检出杂合子419例，纯合子2例，双重杂合子5例。检出13种基因类型，其中CD41—42、CD17、IVS-11—654、CD-28、CD71—72、BE是桂林地区最主要的β-地贫基因突变类型，分别占50．47％、22．30％、12．68％、5。16％、2．81％、2．35％。结论桂林地区β-地贫以中国人发病率高的突变类型为主。     

Evaluation of an aspartame loading test for the detection of heterozygotes for classical phenylketonuria

Classical phenylketonuria (PKU) is an inborn error of metabolism of autosomal recessive inheritance characterized by the accumulation of phenylalanine (Phe) in tissues due to Phe-4-hydroxylase deficiency. Several methods have been developed for the detection of PKU heterozygotes based on the determination of plasma Phe and tyrosine (Tyr) levels, on the analysis of the Phe/Tyr and Phe²/Tyr ratios and on the use of discriminant functions. The objective of the present study was to test the value of loading with aspartame (a sweetener consisting of Phe, aspartate and methanol) for the identification of PKU carriers. The study was conducted on 22 obligate heterozygotes and 27 controls. Two blood samples were collected (under fasting conditions and 30 min after the loading) for fluorometric determination of Phe and Tyr. Phe, Phe/Tyr and Phe²/Tyr values were higher in heterozygotes, whereas Tyr was higher in controls in both situations investigated. Linear discriminant function was considered to be the best parameter for differentiation of the individuals in the two groups. Under the conditions employed in the present study, aspartame loading did not show any advantages in discriminating between PKU carriers and normal individuals when compared to the same analysis performed under fasting conditions.     

Neutral amino acids monitoring in phenylketonuric plasma microdialysates using micellar electrokinetic chromatography and laser-induced fluorescence detection

Neutral and non-polar amino acids such as phenylalanine (Phe), valine (Val), tyrosine (Tyr), threonine (Thre) and GABA are hard to resolve by capillary zone electrophoresis (CZE). Their separation is possible by adding a surfactant to the mobile phase. This method is called micellar electrokinetic chromatography (MEKC). We used MEKC with laser-induced fluorescence detection (LIFD) to separate and quantitate these amino acids in plasma microdialysates of patients with phenylketonuria (PKU). This disease is an inborn enzymatic defect with decreased conversion of Phe to Tyr that causes severe neurological damage and mental deterioration, which is diagnosed by measuring plasma Phe and Phe/Tyr ratio. The amino acids tested had linear concentration-signal relation. PKU patients had significantly higher Phe, lower Tyr, 21 times higher Phe/Tyr ratio and decreased values of Val and Thre than controls. These results show that microdialysis of biological fluids coupled with MEKC-LIFD is a convenient technique to measure neutral amino acids in clinical disorders such as PKU.     

The effect of blood phenylalanine concentration on Kuvan™ response in phenylketonuria

Phenylketonuria (PKU) is caused by mutations in the phenylalanine hydroxylase gene (PAH) with consequent elevation of blood phenylalanine (Phe), reduction in tyrosine (Tyr) and elevation of Phe/Tyr ratio (P/T). Although newborn screening for PKU with early dietary treatment improved severe, irreversible brain damage, older patients suffer reversible losses in executive function when Phe concentrations are elevated. The maintenance of strict nutritional control in older children and adults remains difficult. An adjunct to dietary therapy, oral tetrahydrobiopterin (BH₄) has recently been approved by the Food and Drug Administration as a stable, synthetic BH₄ called Kuvan?. Published studies of Kuvan response in PKU varies and involved primarily children. In this prospective study we evaluated dose–response, response frequency and factors predicting response in 21 patients with PKU (aged 8–30 years), who required life-long dietary treatment. Response to Kuvan was defined at 24 h (acute) and over 4 weeks (chronic) as a ≥ 30% decline in the Phe or P/T ratio. A dose of 20 mg/kg Kuvan was chosen with 29% responding in 24 h and 33% of patients at 4 weeks. We then compared baseline Phe, Tyr, P/T, Phe intake, and frequency of “severe” versus “moderate” mutant PAH alleles among acute and chronic responders and non-responders to Kuvan. Predictors of response to Kuvan, both acute and chronic were baseline Phe and baseline P/T. Baseline Phe and P/T were higher among non-responders (P < 0.05). By contrast baseline Tyr was similar (P = 0.45). Phe intake tended to be higher (18 ± 20 mg/kg/24 h) among Kuvan responders than non-responders (15 ± 11 mg/kg/24 h), P < 0.07 NS. Similarly the frequency of “severe” mutant PAH alleles tended to be more frequent (67%) among non-responders than responders (40%) by Chi² test, P = 0.08 NS. These results were reproducible in a “responder” to Kuvan. To assess directly the effect of elevated blood Phe, Phe was lowered in four, “non-responder” patients, but all failed to respond to Kuvan. We conclude that baseline blood Phe and P/T ratio can predict increased probability for response to Kuvan by patients with classic PKU, but the in vivo mechanisms of response to Kuvan remain enigmatic.     

5-year retrospective analysis of patients with phenylketonuria (PKU) and hyperphenylalaninemia treated at two specialized clinics

BackgroundPhenylketonuria (PKU) is an autosomal recessive disease caused by mutations in the PAH gene, resulting in deficiency of phenylalanine hydroxylase (PAH), an enzyme that converts phenylalanine (Phe) to tyrosine (Tyr). The purpose of this study was to capture real-world data associated with managing PKU under current standard of care and to characterize a representative population for a planned gene therapy trial.MethodsA retrospective chart review was conducted at two U.S. clinics for individuals 10–40 years old diagnosed with PKU-related hyperphenylalaninemia (HPA). Demographics, medical history, treatments and blood Phe data were collected from electronic medical records spanning a five-year period ending in November 2017.Results152 patients were enrolled (65.8% had classical PKU). Although >95% of patients were prescribed a Phe-restricted diet, blood Phe concentrations remained substantially elevated, particularly in patients diagnosed with classical PKU. As the Phe threshold was lowered (Phe < 600, 360, 120 or 30 μmol/L), the number of patients with consecutive lab values below the threshold decreased, suggesting that many patients' Phe levels are inadequately controlled. 62.5% of patients were reported as having a history of at least one neuropsychiatric comorbidity, and adults were more likely than adolescents (69.5% vs. 54.3%). 92 of 98 PAH genotypes collected were distinct mutations; the 6 null-null genotypes were associated with classical PKU. Overall the demographics and clinical data were consistent across both sites.ConclusionDespite dietary restrictions, mean Phe concentrations were > 360 μmol/L (a level considered well-controlled based on current U.S. treatment guidelines) for mild, moderate, and classical PKU patients. There remains an unmet need for therapies to control Phe concentrations.     

Event-related potential correlates of selective processing in early- and continuously-treated children with phenylketonuria: Effects of concurrent phenylalanine level and dietary control

This study focused on important characteristics of attentional (selective) processing in children with early-treated phenylketonuria (PKU). Seven to 14-year-old children with PKU were allocated to high phenylalanine (Phe) and low Phe groups and compared with control children on amplitudes and latencies of early and late event-related potential (ERP) components elicited during a selective processing task. These components are thought to measure early sensory processes (stimulus encoding/perception) and later selection processes (target detection). The effects of concurrent Phe level and dietary control on brain activity and behavioural performance were studied. Results showed that children with PKU with high Phe levels were less accurate and made more false alarms than controls and children with PKU with low Phe levels. Both children with PKU and controls displayed the expected early fronto-central selection negativity and a late positive peak over posterior sites associated with sensory aspects of the selective attention task. However, in contrast with controls, children with PKU showed an absence of condition differences for selection positivity over anterior sites associated with target detection. Negative and positive selection potentials over fronto-central sites were dependent on concurrent and historical Phe levels, whereas sensory potentials depended more strongly on historical Phe levels. It is concluded that both sensory and selection aspects of attention are affected by Phe levels. The relative predictive strength of historical Phe levels suggests that high Phe levels during sensitive periods for brain maturation may have long-lasting influences on selective attention.     

Systematic Review and Meta-Analysis of Neuropsychiatric Symptoms and Executive Functioning in Adults With Phenylketonuria

This systematic review and meta-analysis (MA) investigates the impact of elevated blood phenylalanine (Phe) on neuropsychiatric symptoms in adults with phenylketonuria (PKU). The meta-analysis of PKU is challenging because high-quality evidence is lacking due to the limited number of affected individuals and few placebo-controlled, double-blind studies of adults with high and low blood Phe. Neuropsychiatric symptoms associated with PKU exceed general population estimates for inattention, hyperactivity, depression, and anxiety. High Phe is associated with an increased prevalence of neuropsychiatric symptoms and executive functioning deficits whereas low Phe is associated with improved neurological performance. Findings support lifelong maintenance of low blood Phe.     

Reversal of metabolic and neurological symptoms of phenylketonuric mice treated with a PAH containing helper-dependent adenoviral vector

Phenylketonuria (PKU) is one of the most common inborn errors of metabolism and is due to a deficit of phenylalanine hydroxylase, the enzyme that converts phenylalanine (Phe) into tyrosine (Tyr). The resultant hyperphenylalaninemia (HPA) leads to severe neurological impairment, whose pathogenesis has not been entirely elucidated. Treatment of PKU consists essentially in lifelong protein restriction and, in mild cases, in tetrahydrobiopterin supplementation. However, compliance to both strategies, particularly to the long-term diet, is low and therefore other therapies are desirable. We explored a gene therapy approach aimed at long-term correction of the pathologic phenotype of BTBR-PahEnu2 mice, a mouse model of PKU. To this aim, we developed a helper-dependent adenoviral (HD-Ad) vector expressing phenylalanine hydroxylase and administered it to 3-week-old PKU mice. This resulted in complete normalization of Phe and Tyr levels and reversal of coat hypopigmentation that lasted throughout the observation period of six months. The spatial learning deficits observed in PKU mice were also reversed and hippocampus levels of the N-methyl-D-Aspartate and 2-amino-3-(5-methyl-3-oxo-1,2- oxazol-4-yl) propanoic acid receptor subunits returned to normal. Long-term potentiation, which is impaired in PKU mice, was also restored by treatment. Therefore, HD-Ad vector-mediated gene therapy is a promising approach to PKU treatment.     

Variability in phenylalanine control predicts IQ and executive abilities in children with phenylketonuria

A number of studies have revealed significant relationships between cognitive performance and average phenylalanine (Phe) levels in children with phenylketonuria (PKU), but only a few studies have been conducted to examine the relationships between cognitive performance and variability (fluctuations) in Phe levels. In the current study, we examined a variety of indices of Phe control to determine which index best predicted IQ and executive abilities in 47 school-age children with early- and continuously-treated PKU. Indices of Phe control were mean Phe, the index of dietary control, change in Phe with age, and several indices of variability in Phe (standard deviation, standard error of estimate, and percentage of spikes). These indices were computed over the lifetime and during 3 developmental epochs (< 5, 5.0–9.9, and ≥ 10 years of age). Results indicated that variability in Phe was generally a stronger predictor of cognitive performance than other indices of Phe control. In addition, executive performance was better predicted by variability in Phe during older than younger developmental epochs. These results indicate that variability in Phe should be carefully controlled to maximize cognitive outcomes and that Phe control should not be liberalized as children with PKU age.     

Biochemical phenotype and its relationship with genotype in hyperphenylalaninemia heterozygotes.

The molecular detection of heterozygotes for hyperphenylalaninemia is difficult due to the large number of mutations in the PAH gene. For this reason, various indexes that measure plasma concentrations of phenylalanine (Phe) and tyrosine (Tyr), as an expression of Phe metabolizing capacity, have been used for the detection of carriers for mutations in the PAH gene. In this study, we contrast the biochemical and the molecular data in order to know if this is an accurate method. Familial genetic analysis of the PAH gene in 93 parents of hyperphenylalaninemia patients allows the study of the biochemical expression of the different mutant alleles. Molecular study was performed by SSCP and DGGE analyses of PAH genes, and plasma amino acid analysis by ion-exchange chromatography. Then the biochemical and molecular data were compared by the Student t test. The results found show a relationship between the severity of PKU/HPA mutations in the PAH gene and their biochemical phenotype (Phe/Tyr, Phe2/Tyr) as an expression of the residual enzymatic activity. The study adds further information about the prevalent Mediterranean allele mutations.