Molecular basis of phenylketonuria and related hyperphenylalaninemias: mutations and polymorphisms in the human phenylalanine hydroxylase gene.

Mutations in the human phenylalanine hydroxylase gene producing phenylketonuria or hyperphenylalaninemia have now been identified in many patients from various ethnic groups. These mutations all exhibit a high degree of association with specific restriction fragment-length polymorphism haplotypes at the PAH locus. About 50 of these mutations are single-base substitutions, including six nonsense mutations and eight splicing mutations, with the remainder being missense mutations. One splicing mutation results in a 3 amino acid in-frame insertion. Two or 3 large deletions, 2 single codon deletions, and 2 single base deletions have been found. Twelve of the missense mutations apparently result from the methylation and subsequent deamination of highly mutagenic CpG dinucleotides. Recurrent mutation has been observed at several of these sites, producing associations with different haplotypes in different populations. About half of all missense mutations have been examined by in vitro expression analysis, and a significant correlation has been observed between residual PAH activity and disease phenotype. Since continuing advances in molecular methodologies have dramatically accelerated the rate in which new mutations are being identified and characterized, this register of mutations will be updated periodically.     

In vitro and in vivo correlations for I65T and M1V mutations at the phenylalanine hydroxylase locus.

Mutations at the phenylalanine hydroxylase (PAH) locus are the major cause of hyperphenylalaninemia. We have previously described four mutations (M1V, IVS12nt1, R408W, and S349P) at the PAH locus in French Canadians with ancestry in eastern Quebec. Here we report (1) identification of another mutation, on a haplotype 9 chromosome, which converts codon 65 from isoleucine (ATT) to threonine (ACT), (2) expression analysis of the I65T mutation in COS cells demonstrating 75% loss of both immunoreactive protein and enzyme activity, and (3) expression analysis of the most prevalent PKU allele (M1V) in eastern Quebec, showing nondetectable levels of PAH protein and activity, a finding compatible with a mutation in the translation initiation codon. Homozygosity for M1V and codominant inheritance of I65T/R408W were both associated with classical phenylketonuria.     

2022年度遵义市67403例新生儿苯丙酮尿症筛查分析

目的：分析2022年遵义市67 403例新生儿苯丙酮尿症筛查结果。方法：选取2022年1月至2022年12月在遵义市出生并接受苯丙酮尿症筛查的67 403例新生儿为研究对象,收集其足跟血干血斑样本,采用荧光分析法测定干血斑中新生儿的苯丙氨酸指标水平,疑似阳性的新生儿进行进一步确诊。分析所有新生儿的苯丙酮尿症诊断情况。结果：2022年遵义市69 394例新生儿中总共有67 403例接受了苯丙酮尿症筛查,筛查率为97.13%,其中苯丙酮尿症的可疑阳性数为390例,可疑阳性召回率为100.00%。390例可疑阳性的新生儿中,确诊苯丙酮尿症的有7例,其中男性2例,女性5例,确诊率为0.010 39%。7例患儿中经典型苯丙酮尿症、中度苯丙酮尿症以及轻度高苯丙氨酸血症分别为1例（14.29%）、1例（14.29%）、5例（71.43%）。结论：2022年贵州省遵义市新生儿苯丙酮尿症筛查率为97.13%,苯丙酮尿症发生率为0.010 39%。     

湖南省新生儿先天性甲状腺功能减低症和苯丙酮尿症的筛查分析

目的：了解湖南省新生儿先天性甲状功能减低症（CH）和苯丙酮尿症（PKU）的发病情况,早期诊断和治疗。方法：采用时间分辨荧光免疫法（DELFIA）测定促甲状腺素（TSH）浓度,使用盖塞利细菌抑制法或荧光法测定血苯丙氨酸（Phe)浓度。对TSH≥20μU/L或Phe≥0.26mmol/L(2mg/dl)者,进行确诊检查,确诊后给予治疗并随访。结果：湖南省部分地区46323例新生儿,确诊为CH28例（包括3例TSH延期上升型CH）,PKU患儿1例。经治疗随访患者智能体格发育正常。结论：新生儿筛查能早期发现PKU和CH患儿,及时诊断、治疗和预防智力低下发生,值得大力推广。     

Relation between genotype and phenotype in Swedish phenylketonuria and hyperphenylalaninemia patients

Phenylketonuria (PKU) and hyperphenylalaninemia (HPA) are caused mostly by an inherited (autosomal recessive) deficiency in hepatic phenylalanine hydroxylase (PAH) activity. More than 50 PAH mutations have ben reported. The goal of the present study was to examine the molecular basis for the clinical heterogeneity of Swedish PKU and HPA patients. Mutations were identified through allele-specific oligonucleotide hybridization or DNA sequencing on 128 of the 176 mutant alleles (73%). Three mutations (R408W, Y414C and IVS12) together accounted for 56% of all mutant alleles and ten relatively infrequent mutations were found on another 17% of all mutant alleles. Patients from 50 of the 88 families (57%) had identified mutations in both PAH genes and allowed use to compare the clinical effects of different combinations of PAH mutations. The in vitro activity of all of these mutations, including the newly identified G272X and L364, have been tested in a eukaryotic expression system. There was a strong relationship between the average in vitro PAH activity of the two mutant enzymes and both the phenylalanine tolerance and the neonatal pretreatment serum phenylalanine concentration. This confirms previous observations in Danish and German PKU patients that disease phenotype is a consequence of the nature of the mutations at the PAH locus and not significantly influenced by other loci. The sample population in the previous study did not, however, include mild HPA patients, and the observed correlation is thus restricted to severe and moderate mutant alleles. Since a comparatively high proportion of the Swedish patients were mildly affected, we have provided additional evidence that this correlation is valid throughout a continuous spectrum of clinical varieties. PAH genotyping could therefore help predict prognosis of a recently diagnosed PKU or HPA child.     

Mutational spectrum of the phenylalanine hydroxylase gene in patients with phenylketonuria in the central region of China

Phenylketonuria (PKU, OMIM 261600) caused by phenylalanine hydroxylase (PAH) deficiency is an autosomal recessive disease that is characterized by abnormalities of phenylalanine metabolism. In this study, a total of 77 patients, originating from the central region of China and who were diagnosed with PAH deficiency at the third affiliated hospital of Zhengzhou University, were enrolled in this study. The 13 exons and 12 flanking introns of the PAH gene were analyzed by Sanger sequencing and next generation sequencing. The sequencing data were aligned to the hg19, PAHvdb and HGMD databases to characterize the genotypes of PKU patients, and genotype–phenotype correlations and BH4 responsiveness predictions were performed using BIOPKUdb. In total, 149 alleles were characterized among the 154 PKU alleles. These mutations were located in exons 2–13, and intron 12 of the PAH gene, with a relative frequency of ≥5%, for EX6-96A>G, p.R241C, p.R243Q, p.V399V and p.R53H. Additionally, a novel variant, p.D84G, was identified. The genotype correlated with clinical symptoms in 33.3–100% of the cases, depending on the disease severity, and BH4 responsiveness predictions show that only five patients with MHP-PKU and one patient with Mild-PKU were predicted to be BH4 responsive. In conclusion, we have characterized the mutational spectrum of PAH in the central region of China and have identified a novel mutation. The hotspot mutation information might be useful for screening, diagnosis and treatment of PKU.     

安徽省174例苯丙酮尿症患儿智力发育及其影响因素分析

目的 对安徽省174例苯丙酮尿症(phenylketonuria,PKU)患儿的智力发育情况进行分析,以了解PKU患儿智力发育水平及其相关因素.方法 以安徽省妇幼保健所新生儿疾病筛查中心诊治的174例PKU患儿为研究对象,收集患儿病历中最近1次的智力测试结果、出生和治疗等相关信息,并对患儿监护人进行问卷调查.结果 起始治疗月龄＜3个月的PKU患儿与起始治疗月龄≥3个月的患儿发育商得分和大运动、精细动作、适应能力、语言、社交行为5个领域的得分差异均有统计学意义(均有P＜0.05);多因素Logistic回归分析表明,父母亲文化程度高、家庭年收入高的患儿智力发育商得分较高;起始治疗月龄较大的PKU患儿发育商得分较低.结论 早期治疗的苯丙酮尿症患儿智力发育好,家庭因素对患儿的智力发育也有重要影响.     

内蒙古自治区2010-2018年新生儿PKU和CH筛查情况分析

目的：总结内蒙古自治区2010年到2018年新生儿遗传代谢病筛查以来苯丙酮尿症(PKU)和先天性甲状腺功能减低症(CH)的筛查情况,与全国多地的筛查情况对比,探讨内蒙古地区新生儿遗传代谢病筛查存在的问题及未来发展对策。方法：由内蒙古自治区新生儿疾病筛查中心获得PKU和CH的筛查数据。所有筛查对象在出生后72h针刺足跟采血。PKU采用时间分辨免疫荧光法测定血液苯丙氨酸浓度,CH筛查采用时间分辨免疫荧光分析法测定促甲状腺素浓度。结果：内蒙古2010年至2018年期间,共对834868例新生儿进行了PKU和CH筛查,平均筛查率为42.77%,PKU和CH初筛阳性召回率为84.02%和85.02%,共检出患儿106例(确诊率为1/7876),检出CH患儿207例(确诊率为1/4033)。与国内多地比较,内蒙古地区筛查覆盖率和召回率相对较低,PKU发生率相对较高,CH发生率相对较低。结论：内蒙古自治区新生儿疾病筛查有效预防了PKU和CH导致的出生缺陷,目前筛查覆盖度和召回复查率与国内大部分地区相比较低,应加强管理和宣传,通过多种途径提高新生儿疾病筛查率和复查率。     

The Adolescent Adjustment Profile (AAP) in comparisons of patients with obesity,phenylketonuria or neurobehavioural disorders

Psychosocial development in children with chronic disease is a key issue in paediatrics. This study investigated whether psychosocial adjustment could be reliably assessed with the 42-item Adolescent Adjustment Profile (AAP) instrument. The study mainly focused on adjustment-to-obesity measurement, although it compared three patient groups with chronic conditions. All phenylketonuria (PKU) patients in Sweden between ages 9 and 18 and their parents and teachers were invited to participate. Patients with neurobehavioural syndromes and obesity were age- and gender-matched with PKU patients. Healthy children constituted a reference group. Psychosocial adjustment was measured using the AAP, which is a multi-informant questionnaire that contains four domains. Information concerning parents’ socio-economic and civil status was requested separately. Respondents to the three questionnaires judged the PKU patients to be normal in all four domains. Patients with neurobehavioural syndromes demonstrated less competence and the most problems compared with the other three groups. According to the self-rating, the parent rating and the teacher rating questionnaires, obese patients had internalizing problems. The parent rating and the teacher rating questionnaire scored obese patients as having a lower work capacity than the reference group. Compared with the reference group, not only families with obese children but also families with children with neurobehavioural syndromes had significantly higher divorce rates. Obese patients were also investigated with the Strength and Difficulties Questionnaire (SDQ), another instrument that enables comparison between two measures of adjustment. The AAP had good psychometric properties; it was judged a useful instrument in research on adolescents with chronic diseases.