婴儿肝内胆汁淤积症SLC25A13基因突变分析

目的 探讨SLC25A13基因突变在中国婴儿肝内胆汁淤积症患儿中的检出率，初步了解突变患儿血生化及氨基酸谱特征，肝脏活组织病理变化。方法 2003年12月至2006年12月就诊于复旦大学附属儿科医院的婴儿肝内胆汁淤积症患儿，满足本研究入选条件者共115例进行了血氨基酸质谱分析，伴血浆瓜氨酸明显升高的患儿进行SLC25A13基因全部外显子及邻近序列测序，不伴血浆瓜氨酸明显升高的患儿进行SLC25A13基因常见突变851del4（突变Ⅰ）及突变1638ins23（突变Ⅲ）筛查，突变851del4采用实时荧光定量PCR双标记探针法检测，突变1638ins23采用PCR产物直接电泳法检测，对仅检出单个位点突变的筛查对象，继续进行其余已报道的10种突变位点检测。检测结果仍为单个杂合突变的对象进行SLC25A13基因所有外显子区及其邻近序列分析。对确诊突变患儿的临床表现、血生化及血氨基酸特征等进行分析。结果5例伴血瓜氨酸明显升高的患儿共检出突变4例，其中纯合突变851del4/851del4 1例，复合杂合突变851del4/1638ins23 1例，杂合突变851del4 2例；110例不伴血浆瓜氨酸明显升高患儿共检出突变6例，其中纯合突变851del4/851del4 1例，复合杂合突变851del4/1638ins23 1例，杂合突变851del4 4例。115例婴儿肝内胆汁淤积症患儿共检出SLC25A13基因突变10例，占8.7％。突变患儿血生化改变包括胆红素、γ-谷氨酰转移酶以及碱性磷酸酶等明显升高，AST升高较ALT明显。血串联质谱发现5例突变患儿有特征性氨基酸瓜氨酸、苏氨酸及蛋氨酸升高，另5例突变患儿并无血氨基酸改变。10例患儿中有7例行肝脏活组织病理学检查，4例有显著的脂肪变性。结论 SLC25A13基因突变是中国婴儿肝内胆汁淤积症的重要原因之一。肝脏活组织病理、血生化及氨基酸谱等检查对诊断SLC25A13基因突变患儿有重要意义，但最终仍需通过基因检测确诊。

SLC25A13 gene mutation in infants with intrahepatic cholestasis

Objective To explore the prevalence of SLC25A13 gene mutations in Chinese infants with intrahepatic cholestasis and to understand the clinical presentation,laboratory biochemistry and blood amino acids features of patients with mutations.Methods Blood amino acids were analyzed by using mass chromatography in 115 infants who were referred to our hospital for further investigations of intrahepatic cholestasis from December 2003 to December 2006. All exons and their neighbouring sequences of SLC25A13 gene were analysed in children whose plasma citrulline obviously elevated. Two most common mutations of SLC25A13 gene, 851del4 and 1638ins23 were screened in children without obvious citrullinemia. Mutation 851del4 was detected by real time fluorescent quantitation PCR with double labelling probes, and mutation 1638ins23 was detected by electrophoresis of PCR product directly. If the children in whom only one heterozygous mutation was found, all exons and nearby sequences were analysed then after. Clinical presentation,laboratory biochemistry and blood amino acids examinations were analyzed.ResultsSLC25A13 gene mutations were found in 4 of 5 children with citrullinemia, including 1 patient with homozygous mutation 851del4/851del4, 1 patient with compound heterozygous mutation 851del4/1638ins23, and 2 patients with heterozygous mutation 851del4. SLC25A13 gene mutations were also found in 6 cases of the other 110 intrahepatic cholestasis patients, including 1 patient with homozygous mutation 851del4/851del4, 1 patient with compound heterozygous mutation 851del4/1638ins23, and 4 patients with heterozygous mutation 851del4. Totally, SLC25A13 gene mutations were detected in 10 of the 115 intrahepatic cholestasis patients. The prevalence rate was 8.7％. Liver biopsy was done in 7 of 10 children with SLC25A13 gene mutations, and significant steatosis was found in 4 of them. Laboratory biochemistry changes included obviously elevation of bilirubin,γ glutamyl transpeptidase and alkaline phosphatase. The elevation of aspartate aminotransferase was more obvious than alanine aminotransferase. Characteristic amino acids such as citrulin,threonine and methionine elevation was found in 5 children with mutations.Conclusions SLC25A13 gene mutation was one of the important causes of Chinese infantal intrahepatic cholestasis. Liver biopsy, laboratory biochemistry, and blood amino acids examination were important for the diagnosis of SLC25A13 gene mutations, however, the final diagnosis must rely on gene detection.