摘要
目的分析2例酪氨酸血症Ⅰ型患儿临床表现及FAH基因突变。方法按照国际罕见病组织提供的诊断标准筛选2例患儿，采用PCR直接测序技术对患儿FAH基因的14个外显子及邻近片段进行序列分析，在其父母中间进行突变的验证，Clustal X软件分析物种问FAH酶的同源性。Polyphen软件通过计算特定位置独立计数得分（PSIC）预测突变意义。结果例1男，5个月21d，迁延性腹泻，肝脾肿大、腹部移动性浊音；甲胎蛋白〉1210μg／L，血酪氨酸110．8μmol／L，尿琥珀酰丙酮83．7μmol／L；同胞中姐姐因慢性腹泻就诊，疑酪氨酸血症Ⅰ型。FAH基因分析示第5外显子455位碱基G变为A（c．455G〉A），导致在152位形成终止密码子（W152X），第12外显子1027位碱基G变为A（c．1027G〉A），导致第343位氨基酸由甘氨酸变为精氨酸（G343R），即c．455G〉A／c．1027G〉A复合杂合突变。例2女，6岁1个月，晚发型佝偻病起病，身高及体重在同龄儿数值的第3百分位以下，肝脾肿大，串珠肋、手足镯、双膝向右侧弯曲，血磷0．54-1．09mmol／L，血钙2．41mmol／L，碱性磷酸酶1620IU／L，甲胎蛋白412.8ug/L，血酪氨酸835．8μmol／L，尿琥珀酰丙酮27．48μmol／L。钙剂及维生素D3治疗无效。患儿父母为近亲婚配。FAH基因测序示C．1027G〉A／c．1027G〉A纯合突变。2例患儿父母均为杂合突变携带者。Clustal X预测突变为高度保守，Polyphen软件计算c．1027G〉A突变的PSIC得分为3．235，为致病突变。结论酪氨酸血症Ⅰ型患儿可以迁延性腹泻或晚发型佝偻病起病，肝脾肿大，难以纠正的低磷血症，甲胎蛋白明显升高，有家族史或父母近亲婚配史，尿琥珀酰丙酮异常，FAH基因检测有c．455G〉A和c．1027G〉A突变。
Objective To investigate the clinical features and mutations of the FAH gene. Method Clinical records of two cases were collected, and diagnosis was made according to the diagnostic criteria of the International Organization for Rare Disorders （NORD）. Genomic DNA was extracted from peripheral blood leukocytes with QIAamp DNA Mini Kit. The DNA extracts were subjected to direct sequencing for 14 exons together with adjacent fragments of bAH gene using ABI Prism 3730 Genetic Analyzer （ Applied Biosystems, Foster City, CA ） after PCR based on genomie DNA. The mutation source was verified by analyzing parents＇ exons corresponding to patients＇ mutation exons. The homology between human FAH enzyme and that of other species was surveyed using software Clustal X （ European Bioinformatics Institute, Hinxton, Saffron Walde, UK）. Polyphen （Polymorphism Phenotyping）, available online, were used to predict possible impact of an amino acid substitution on structure and function of FAH enzyme. Polyphen calculates position-specific independent counts （PISC） scores for two amino acid variants in polymorphic position. A PISC scores that differ by 〉 2 were regarded as indicating the probability of damaging variants. Result Patient 1 was a 5 months and 21 days-old boy who suffered from persistent diarrhea, hepatomegaly, ascites; Alpha-fetoprotein 〉 1210μg/L, levels of tyrosine in blood and succinylacetone in urine were 110. 8 μmol/L and 83.7μmol/L. His sister suffered from tyrosinemia type 1. Direct sequencing showed a G to A transition in CDS position 455 and 1027. He was compound heterozygous for the mutation c. 455G 〉 A/c. 1027G 〉 A, which predicts a change from tryptophan to a stop codon （TGG 〉 TAG） at position 152 （W152X） and a change from glycine to arginine （ GGG 〉 AGG） at position 343 respectively. Patient 2 was a 6 year and 1 month-old girl with late-onset rickets who had signs of hepatosplenomegaly, rachitic rosary, windswept knees. Hypophosphatemia and alkaline phosphatase 1620 IU/L were detected. Alpha-fetoprotein 412. 8 μg/L, levels of tyrosine in blood and succinylacetone in urine were 835.8μmol/L and 27. 48 μmol/ L. Rickets did not improve after administration of calcium and vitamine D3. She is homozygous for the mutation c. 1027G 〉 A/e. 1027G 〉 A, which predicts G343R. The parents were mutation carriers. Analysis by Clustal X on the alignment of amino acids residual reservation among different species showed that the locative amino acid was highly conserved. Polyphen software predicted G343R was probably damaging （ PISC score 3. 235 ）. Conclusion Children with tyrosinemia type 1 can have manifestations of persistent diarrhea or late-onset rickets. Physical examination can reveal hepatosplenomegaly, laboratory tests indicate markedly elevated serum concentration of alpha-fetoprotein and alkaline phosphatase in plasma and succinylacetone in urine, other members in family may have tyrosinemias or parents are consanguineous. Mutations c. 455G 〉 A and e. 1027G 〉 A can be detected in FAH gene of Chinese children.
出处
《中华儿科杂志》
CAS
CSCD
北大核心
2013年第4期302-307,共6页
Chinese Journal of Pediatrics
基金
国家自然科学基金（No.81070281）
