四氢生物喋呤负荷试验在高苯丙氨酸血症鉴别诊断中的临床应用

目的探讨四氢生物喋呤（BH4）负荷试验在高苯丙氨酸血症（HPA）鉴别诊断中的应用价值。方法自2005年5月到2007年4月，51例HPA患儿采用口服BH4（20mg／kg）负荷试验。对其中血苯丙氨酸（Phe）浓度小于600μmol／L患儿采用口服Phe—BH4联合负荷试验，结合尿喋呤分析、血红细胞二氢喋呤还原酶（DHPR）活性测定。结果（1）在BH4负荷试验中，不同类型HPA患儿的血Phe浓度表现出各不相同的改变。51例HPA患儿中，共鉴别出5例BH4缺乏症，10例BH4反应性苯丙氨酸羟化酶（PAH）缺乏症，36例BH4无反应性苯丙氨酸羟化酶（PAH）缺乏症。（2）在17例中度苯丙酮尿症（PKU）患儿中，9例（52．9％）为BH4反应性PAH缺乏症。结论BH4负荷试验在HPA早期鉴别诊断中十分重要，部分中度PKU对BH4有反应，可使用BH4替代治疗。     

四氢生物蝶呤反应性苯丙氨酸羟化酶缺乏症在我国南北地区差异的临床初步研究

目的通过对不同类型高苯丙氨酸血症（hyperphenylalaninemia,HPA）临床特点的分析,探讨我国南、北方四氢生物蝶呤（tetrahydrobiopterin,BH4）反应性苯丙氨酸羟化酶（phenylalanine hydroxylase,PAH）缺乏症患者对BH4的反应性。方法（1）108例HPA患儿,男63例、女45例,平均年龄7.05个月。所有患者都进行口服BH4负荷试验,同时进行尿蝶呤谱分析、红细胞二氢蝶啶还原酶测定。对其中血苯丙氨酸（phenylalanine,Phe）浓度〈600μmol/L者给予口服Phe-BH4联合负荷试验。（2）根据患儿父母双方祖籍,以长江为界将诊断为BH4反应性PAH缺乏症的患儿分为南、北两组。比较南、北方组BH4反应性PAH缺乏症患儿在BH4负荷试验中血Phe浓度的变化。结果（1）HPA中诊断BH4反应性PAH缺乏症36人（33.3%）,BH4无反应性苯丙酮尿症（phenlketonuria,PKU）49人（45.4%）,四氢生物蝶呤缺乏症（BH4D）23人（21.3%）。BH4反应性PAH缺乏症血Phe浓度8h、24h时分别平均下降了49.24%和65.35%。（2）36例BH4反应性患者分为南方组23人、北方组13人。南、北方组BH4反应性患儿服药后24h时血Phe浓度均值分别为（217.02±189.03）μmol/L和（458.75±342.54）μmol/L（P〈0.05）,而两者在服药后2h、4h、8h、24h时血Phe浓度下降的百分数差异均无统计学意义（P〉0.05）。结论部分因PAH缺乏引起的PKU患儿口服BH420mg/kg后24h,血Phe浓度较服药前下降30%以上,其中绝大多数为轻、中度HPA（血Phe120～1200μmol/L）,少数为经典型PKU（血Phe〉1200μmol/L）。本研究中我国南方组BH4反应性PAH缺乏症服药24h时血Phe浓度较北方组低,但是南、北方患者对药物的总体反应性差异无统计学意义。     

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。     

高苯丙氨酸血症患儿尿蝶呤谱分析及正常人群尿蝶呤谱参考区间的建立

目的探讨尿蝶呤谱分析、口服四氢生物蝶呤(tetrahydrobiopterin,BH_4)药物负荷试验及酸学分析在高苯丙氨酸血症(hyperphenylalaninemia,HPA)诊断与分型中的意义,同时建立本地区正常人群尿蝶呤谱参考区间,为我国正常人群尿蝶呤谱参考区间的制订提供可靠数据。方法 2014年1月至2017年6月本中心正常健康人群及无先天性遗传代谢缺陷的人群859例为正常对照组,确诊的137例高苯丙氨酸血症患者为研究组,运用串联质谱(LC-MS/MS)测定血苯丙氨酸(Phe)、高效液相色谱(HPLC)对尿液蝶呤谱分析,同时根据BH_4药物负荷试验,红细胞二氢生物蝶啶还原酶(DHPR)进行分组研究,运用统计学进行差异性分析及正常人群各年龄段参考区间建立。结果 137例HPA中,BH_4反应型HPA22例,占16.05%(22/137),无反应型HPA79例,占57.66%(79/137),BH_4缺乏症36例,占26.27%(36/137),其中6-丙酮酰四氢蝶呤合成酶(6-pyruvoyl tetrahydropterin synthase deficiency,PTPS)34例,占BH_4缺乏症94.44%(34/36)例,二氢生物蝶啶还原酶(dilydropterindine reductase deficiency,DHPR)2例,占5.56%(2/36)。尿蝶呤谱PTPS缺乏组年龄差异无统计学意义(P0.05),新蝶呤(neopterin,N)高于正常对照组和无反应型HPA组,生物蝶呤(biopterin,B)及生物蝶呤百分比(B/N+B,B%)明显低于各组,差异有统计学意义(P0.05);BH_4反应型HPA和无反应型HPA组N、B均高于正常对照组,差异有统计学意义(P0.05),而B%差异无统计学意义(P0.05);BH_4反应型HPA与无反应型HPA两组差异无统计学意义(P0.05)。口服BH_4药物负荷试验PTPS组血Phe浓度下降最快并在4h内降至正常,无反应型HPA组24h变化不明显,BH_4反应型HPA和DHPR缺乏组下降速度和幅度相似,但DHPR缺乏组酶活性低于正常。结论尿蝶呤谱分析对BH_4缺乏症分型及鉴别BH_4反应型HPA、无反应型HPA有辅助作用。口服BH_4药物负荷试验能快速判断血Phe对BH_4反应程度、血Phe的变化趋势,为可为HPA患者药物治疗提供依据,同时结合本地区正常人群尿蝶呤谱参考区间,为提高BH_4缺乏症诊断率及制定我国尿蝶呤谱参考值提供可参考依据。     

中国南方四氢生物蝶呤缺乏症筛查、临床及基因突变的系列研究

目的 得出我国南方高苯丙氨酸血症（hyperphenylalaninemia,HPA)者四氢生物蝶呤（tetrahydrobiopterin,BH4)缺乏症的发病率,总结BH4缺乏症者基因突变和临床转归的研究。方法 对87例HPA者做尿新蝶呤（N）和生物蝶呤（B）分析;对BH4缺乏症者进行基因突变检测及治疗随访。结果 11例诊断为6－丙酮酰四氢蝶呤合成酶（PTPS）缺乏所致BH4缺乏症,其尿N／B＞38,B％＜5％,在HPA中其发病率为12％。5例中发现4种PTPS基因突变类型,即P87S、N52S、D96N及G144R（新突变类型）。5例经BH4、L－DOPA及5－羟色氨酸治疗后体格发育良好,4例智商（IQ）70－80分。结论 对所有HPA者需进行BH4缺乏症的筛查,以降低误诊率。     

宝鸡地区2007∽2013年新生儿筛查高苯丙氨酸血症结果分析

目的对宝鸡市2007年∽2013年间的204 868例新生儿筛查苯丙氨酸浓度测定,并对部分阳性患儿血、尿标本进行MS/MS、GS/MS分析,探讨我市PKU发病情况和发病率。方法采用ELISA时间分辨荧光免疫多标记免疫分析法（DELFIA）检测血苯丙氨酸浓度。结果筛查出高苯丙氨酸血症71例,其中经典型PKU17例,轻度PKU22例,轻度HPA30例,BH4缺乏症2例,高HPA检出率为1/2885（71/204868）,高出全国HPA发生率（1/11444）,BH4缺乏症为2.82%。结论开展新生儿筛查是早期发现HPA的有效方法,对HPA患儿应进一步进行鉴别诊断,排除四氢喋呤缺乏症,并进行及时治疗,避免残障儿的发生。     

四氢生物蝶呤反应性的苯丙酮尿症研究进展

本文综述对四氢生物蝶呤（BH4）反应性的苯丙氨酸羟化酶（PAH）基因缺陷的苯丙酮尿症（PKU）的研究进展。分析BH4反应性的PAH基因突变，探讨这一现象潜在的发生机制，介绍一种新的临床分类法，并对PKU的BH4替代治疗前景进行展望。     

中国北方人群四氢生物蝶呤缺乏症的研究

目的探讨中国北方人群四氢生物蝶呤(tetrahydrobiopterin,BH4)缺乏症的筛查、治疗和长期预后。方法自1992年到2005年,我院共诊治主要来自中国北方地区的高苯丙氨酸血症(hyperpheny lalaninemia,HPA)患者618例。采用尿蝶呤谱分析,红细胞二氢蝶啶还原酶(dihydropteridinereductase,DHPR)活性测定及四氢生物蝶呤负荷试验,对这些患者进行BH4缺乏症的鉴别诊断;确诊患者立即进行BH4、左旋多巴和5羟色胺三药联合治疗。定期随诊患者的精神运动和智能发育情况。结果(1)在618例HPA患者中,共鉴别出38例BH4缺乏症,而且皆表现为尿生物蝶呤显著降低,新蝶呤显著增加,红细胞DHPR活性正常,血苯丙氨酸浓度在BH4负荷后4～8小时内降至正常,即全部是6丙酮酰四氢蝶呤合成酶(6pyruvoyl tetrahydropterinsynthase,PTPS)缺乏型,被确诊时的年龄为2岁零1个月～13岁;(2)其中,只有27例患儿接受规律治疗并定期随诊。在经过3个月～10年的治疗后,患者的发育商或智商(developmentorintelligence quotient,DQ/IQ)明显提高(治疗前后分别为52±16,79±15),但智能发育各个方面并不平行;(3)通过对患儿目前DQ/IQ与治疗开始时间进行Pearson相关分析发现,二者呈明显负相关(r=-0.714,P<0.01)。结论对所有HPA患者都必须早期进行BH4缺乏症的鉴别诊断;PTPS缺乏症是中国北方导致BH4缺乏症的主要原因;PTPS缺乏症患者必须进行BH4、左旋多巴和5羟色胺三药联合治疗,而且治疗越早,效果越好。     

1066例高苯丙氨酸血症患者诊断及治疗随访

目的1066例高苯丙氨酸血症（HPA）患者治疗随访。方法自1984年10月到2009年12月,我院共诊治HPA患者1066例。采用高效液相色谱法进行尿喋呤分析,血红细胞二氢喋啶还原酶（DHPR）活性测定及四氢生物喋呤（BH4）负荷试验,进行四氢生物喋呤缺乏症（BH。D）的鉴别;对部分患者进行MRI、1HMRS检查;对不同类型的HPA进行治疗。结果（1）1066例中1016例为苯丙氨酸羟化酶缺乏症（PAHD）,其中51例为BH4反应性PAHD;50例为BH4Dc（2）28例筛查早治的BH4D患儿智商为（96±15）分,晚治疗的11例患儿治疗前为（46±15）分,治疗后为（69±11）分,前后有显著意义（P〈0．05）。DQ／IQ水平与治疗开始时间呈明显的负相关（r=-0．714,P〈0．01）。（3）33例BH4反应性PAHD患儿的智商为（92±18）分。（4）PAHD患者治疗中筛查组智商与非筛查组智商比较,筛查治疗理想组智商与筛查治疗不理想组智商比较,非筛查治疗理想组智商与非筛查治疗不理想组智商比较均有意义（P〈0．001）,47例非新筛并控制理想血Phe浓度PKU患儿智商从治疗前的（60．66±7．78）分,提高到治疗后的（76．62±7．55）分（P〈0．001）。（5）合并癫痫的患儿脑电图的异常率为94．3％,将血苯丙氨酸浓度控制在理想范围,可使脑电图异常有改善。（6）22例大于4个月的患儿血、脑Phe浓度与智商均呈负相关关系r血=-0．5045,r脑=-0．6471（P〈0．01）。结论对所有HPA患者都必须进行BH4D的鉴别诊断,尽早确诊和治疗效果越好。严格控制血苯丙氨酸浓度是减少智能落后的最好措施。     

16例新生儿苯丙酮尿症筛查确诊患儿治疗效果初步分析

目的 对新生儿苯丙酮尿症（PKU）筛查确诊患儿的治疗效果进行初步分析。方法 采用化学荧光分析法或细菌抑制法进行足跟血苯丙氨酸（phe）检测，对高苯丙氨酸症者进行尿碟呤谱分析、红细胞二氢碟啶还原酶（DHPR）活性检测，以及phe加BH。联合负荷试验；PKU患儿用饮食疗法，四氢生物碟呤缺乏症（BH4D）用药物治疗。结果 我省PKU发病率为1：18447，BH4D占55％；接受饮食治疗的PKU患儿7例，其智商〉90分5例，占71．4％，智商50—69分2例，占28．6％；接受药物治疗的BH4D患儿9例，其智商≥90分2例，占22．2％、智商70—84分3例，占33．3％、智商50—69分4例，占44．4％。结论 PKU患儿早期诊疗能达到避免严重弱智的目的。     

Extended tetrahydrobiopterin loading test in the diagnosis of cofactor-responsive phenylketonuria: a pilot study

Patients with tetrahydrobiopterin (BH4)-responsive phenylalanine hydroxylase (PAH) deficiency may benefit from BH4 therapy instead or in addition to the low-phenylalanine diet. Different loading test protocols are currently used to detect these patients. As a consequence, data on the rate of BH4-responsiveness within patients with mild phenylketonuria (PKU) and/or more severe phenotypes show high variation and a more sensitive and standardised BH4 loading test protocol needs to be defined. We modified the current standard BH4 loading test (20 mg/kg) to a second administration of 20 mg/kg after 24 h and extended blood sampling to 48 h in 24 patients with PAH deficiency. Using this extended loading test (2 x 20 mg BH4/kg), the rate of BH4-responsiveness was calculated at 8, 24, and 48 h after BH4 administration. We defined three groups of patients: "rapid responders" in 10/24 patients (4 mild HPA, 2 mild PKU, 2 moderate PKU, and 2 classic PKU), "moderate responders" in 4/24 patients (4 classic PKU), and "slow responder" in 4/24 patients (4 mild PKU). Six out of 24 patients (1 mild HPA, 1 moderate PKU, and 4 classic PKU) were found to be "non-responder." Individual phenylalanine profiles show variations in responsiveness at different time points and sampling over 48 h was more informative than over 24h in patients with mild and moderate PKU compared to mild HPA. Analysis of BH4 loading tests in 209 patients with the standard BH4 loading test protocol confirms only minor importance of the 24 h response: the rate of responsiveness to BH4 after 24 h was shown to be equal to or even lower than after 8h among most phenotypes. However, extension of the BH4 loading test to 48 h and repeated BH4 administration seems to be useful to detect BH4-responsiveness in more severe phenotypes and allows detecting "slow responders" who may benefit from BH4 therapy.     

Long-term treatment of patients with mild and classical phenylketonuria by tetrahydrobiopterin

Tetrahydrobiopterin (BH4), the natural cofactor of phenylalanine hydroxylase (EC 1.14.16.1), can reduce blood phenylalanine (Phe) in BH4 sensitive patients with hyperphenylalaninemia (McKuisick 261600). We report on the long-term treatment of eight patients with mild and classical phenylketonuria (blood Phe levels maximum blood Phe levels between 771 and 1500 micromol/L) using BH4 at a dosage of 8-12 mg/kg BW per day. In all patients reduction of blood Phe was >30% after BH4 loading test. Three patients were treated from birth by BH4 only, five after initial low Phe dietary treatment. Seven of them continue to be on BH4 treatment only, one has a relaxed low protein diet. No side effects could be observed (longest observation time 5 years), somatic and psychomotor development were normal. The main problem of BH4 treatment is finding an optimal dosage at different ages and an under special conditions like infectious diseases. There is evidence that in some patients BH4 treatment may allow a more relaxed low protein diet showing positive effects on weight gain and quality of life. Further controlled studies are necessary not only to rule out any side effects but also for optimizing treatment strategies with BH4 treatment in mild phenylketonuria.     

Positive effect of a simplified diet on blood phenylalanine control in different phenylketonuria variants, characterized by newborn BH4 loading test and PAH analysis

Until today, the mainstay of phenylketonuria (PKU) treatment is a phenylalanine (Phe)-restricted diet. Strict dietary treatment decreases flexibility and autonomy and still has a major impact on patients and their families. Compliance is often poor, particularly in adolescence. The aim of this study was to investigate the effect of the intake of fruits and vegetables containing Phe less than 100 mg/100g ('simplified diet'), as recommended by WHO for all individuals, instead of classical totally restricted diet on the course and treatment control of the disease in a well-characterized PKU cohort (n=80). All individual blood Phe measurements of each patient (1992-2009) were statistically analyzed before and after diet switch. Epidemiological data, age at diagnosis, PAH mutations, BH(4) responsiveness, as well as Phe control measurements and detailed diet information were tabulated in a local database. 62.5% had BH4 loading test and 40% had PAH analysis; 50/80 switched from classical to simplified diet, including 26 classical PKU, 13 moderate PKU, 7 mild PKU and 4 mild hyperphenylalaninemia (HPA). Median Phe levels on a simplified diet did not differ significantly to the median Phe levels on classical diet in all disease groups. Our results indicate that a simplified diet has no negative effect on blood Phe control in patients with hyperphenylalaninemia, independent of severity of the phenotype or the age at diet switch, over the period of 3 years. Thus, a simpler approach to dietary treatment of PKU available to all HPA patients is more likely to be accepted and adhered by patients and might also increase quality of life.     

High frequency of tetrahydrobiopterin-responsiveness among hyperphenylalaninemias: a study of 1,919 patients observed from 1988 to 2002

Tetrahydrobiopterin (BH(4))-responsive hyperphenylalaninemia (HPA) is a recently described variant of phenylalanine hydroxylase deficiency. In contrast to patients with classical phenylketonuria, these patients respond to BH(4) loading tests (20mg/kg) with decrease of plasma phenylalanine levels 4 and 8 h after administration and they can be treated with BH(4) monotherapy. We retrospectively evaluated 1,919 loading tests from 33 different countries performed in our laboratory between 1988 and 2002 of which 278 loading tests were performed with 6R-BH(4), which is about 33% more active than the formerly used 6R,S-BH(4). The loading tests were performed between the ages of one week and 4.6 years, using 2.6-30.0 mg 6R,S- or 6R-BH(4)/kg. Plasma phenylalanine levels before the test ranged from 121 to 4,705 micromol/L. We calculated the phenylalanine "hydroxylation rate" 4 and 8 h after BH(4) administration and plotted the slope of the hydroxylation rate against the phenylalanine levels at time 0. The slope was greater than 3.75 in 65, 74, 33, 17, 0, and 10% of patients with basal phenylalanine levels of 120-400, 400-800, 800-1,200, 1,200-1,600, 1,600-2,200, and >2,200 micromol/L, respectively, when loaded with 20 mg 6R-BH(4)/kg (p>0.0001). This is 5-20 times higher compared with tests using 6R,S-BH(4) or lower doses of BH(4). More than 70% of patients with mild HPA (<800 micromol/L) are found to be BH(4) responders. Therapy with BH(4) (approximately 10mg/kg/day) was initiated in several patients instead of a low-phenylalanine diet, resulting in much better treatment compliance. Our data further demonstrate that BH(4) loading tests can only distinguish between BH(4) responders and non-responders. To differentiate between BH(4) and phenylalanine hydroxylase deficiencies additional tests are essential.     

Tetrahydrobiopterin sensitivity in German patients with mild phenylalanine hydroxylase deficiency

We report the results of tetrahydrobiopterin (BH4) loading tests in 10 German patients with mild phenylketonuria. A significant decline of phenylalanine values after application of BH4 was observed in all but one patients. Molecular genetic analyses revealed a range of different PAH gene mutations. Re-testing of one patient previously reported as non-responsive to BH4 loading showed a moderate response with a higher dose of BH4. Nevertheless, there appear to be kinetic differences in phenylalanine hydroxylation in patients with the same genotype. Non-responsiveness to 20 mg/kg BH4 was observed only in a single patient who was compound heterozygous for the novel mutation R176P (c.527G>C) and the common null-mutation P281L. In summary, our data are in line with recent reports indicating that BH4 sensitivity is a normal feature of most mild forms of PAH deficiency but may be influenced by other factors.     

Tetrahydrobiopterin responsiveness: results of the BH4 loading test in 31 Spanish PKU patients and correlation with their genotype

Tetrahydrobiopterin (BH4) responsiveness in patients with mutations in the phenylalanine hydroxylase (PAH) gene is a recently recognized subtype of hyperphenylalaninemia characterized by a positive BH4 loading test. According to recent estimates, this phenotype may be quite common, suggesting that a large group of individuals may benefit from BH4 substitution, eliminating the need of life-long dietary restrictions. This underscores the importance of identifying BH4-responsive patients in each population, establishing the association with specific PAH mutations. In this work, we describe the results of a pilot study performed with 31 Spanish PAH-deficient patients subjected to a BH4 loading test. Overall, 11/31 (37%) showed a positive response with a 30% decrease in blood Phe levels 8 h after the BH4 challenge, and three additional patients, considered slow responders, showed this decrease only after 12-16 h. We report for the first time a patient homozygous for a splicing mutation with a slow response, suggesting an effect of BH4 supplementation on PAH gene expression. Most of the responsive patients belong to the mild hyperphenylalaninemia (MHP) or mild phenylketonuria phenotypic groups. In MHP patients we report for the first time the results of parallel single Phe doses confirming the utility of these analyses for a better evaluation of the response. Genotype analysis confirms the involvement in the response of specific mutations (D415N, S87R, R176L, E390G, and A309V) present in hemizygous patients, and provide relevant information for the discussion of the potential mechanisms underlying BH4 responsiveness.     

Long-term follow-up of a patient with mild tetrahydrobiopterin-responsive phenylketonuria

We report on the long-term follow-up of the first Italian patient with the tetrahydrobiopterin (BH4)-responsive type of phenylalanine hydroxylase deficiency (R243X/Y414C genotype). The patient was diagnosed by the newborn screening for phenylketonuria (PKU) and with a positive BH4 loading test. Introduction of BH4 (initially 10 and later 20 mg/kg/day) in addition to reduced low-phenylalanine diet resulted in therapeutic plasma phenylalanine concentrations (<340 micromol/L). Very good compliance and no side effects in this patient demonstrate the great potential of BH4 in the treatment of some patients with mild PKU.