串联质谱技术在有机酸血症鉴别诊断中的应用

Study of application of the tandem mass spectrometry in the differential diagnosis of organic acidemias

目的探讨串联质谱技术在有机酸血症诊断和鉴别诊断中的作用。方法对2566例遗传性代谢病高危儿童的干血滤纸片进行串联质谱分析,结合尿气相色谱质谱有机酸分析、酶活性测定和基因突变分析,诊断有机酸血症。比较不同有机酸血症间的串联质谱结果差异。结果共确诊有机酸血症82例(3.2%),其中甲基丙二酸血症(MMA)44例,丙酸血症(PA)10例,生物素酶缺乏症4例和全羧化酶合成酶缺乏症2例;患儿丙酰肉碱(propinoylcar-nitine,C3)水平均高于健康儿童上限值(4.0μmol/L)。PA和MMA患儿C3与游离肉碱(C0)比值(C3/C0)、C3与乙酰肉碱(C2)比值(C3/C2)也高于健康儿童上限值;PA患儿同时伴有甘氨酸增高,甲基丙二酸血症患儿甘氨酸正常;生物素酶缺乏症和全羧化酶合成酶症患儿伴3"羟基"异戊酰肉碱(3"hydyoxyl"isovalerylcarnitine,C5"OH)水平增高;3"甲基巴豆酰辅酶A羧化酶缺乏症(5例)、3"羟基"3"甲基戊二酰辅酶A裂解酶缺乏症(3例)和β"酮硫解酶缺乏症(4例)患儿C5"OH水平也增高,前两种疾病仅表现为C5"OH增高,后一种疾病同时伴有异戊烯酰基肉碱水平增高;异戊酸血症5例,仅表现为异戊酰肉碱(C5)增高;戊二酸血症(GA)"Ⅰ型(3例)仅表现为戊二酰肉碱(C5DC)增高,GA"Ⅱ型(2例)除C5DC增高外,伴有多种酰基肉碱增高,两者可作鉴别。结论通过串联质谱酰基肉碱、酰基肉碱比值和氨基酸分析,可对部分有机酸血症进行诊断和鉴别诊断;部分有机酸血症需结合尿气相色谱质谱有机酸分析进行诊断。

Objectives To investigate the effect of tandem mass spectrometry on the differential diagnosis of organic acidemias. Methods Combined with gas- chromatography mass spectrometry,enzymetic activity determination,genomic mutation analysis, tandem mass spectrometry was used for 2 566 children with high risk of genetic inborn metabolism diseases to confirm the diagnosis of organic acidemias. The resuhs were also compared among the patients with different diseases. Results Eighty-two patients were diagnosed as organic academia, including 44 patients with methylmalonic academia （MMA）, 10 with propionic academia（PA）,4 with biotinidase deficiency （BTD）,and 2 with holocarboxylase sythetase deficiency . The propinoylcarnitine （C3） level in all these patients was higher than the upper limit value of normal control （4.0 μmol/L）. The ratio of C3/C0 （free carnitine）and C3/C2（acytylcarnitine）also exceed the upper limit normal level in patients with PA and MMA. The level of glycine was also elevated in PA patients, but normal in MMA patients. While the 3-hydyoxyl- isovalerylearnitine （C5-OH） level increased signitieantly in the patients with BTD and holocarboxylase synthetase deficiency. In addition ,increased C5- OH were also identified in patients with 3- methyl- crotonyl - CoA carboxylase deficiency （MCC, 5 cases ）, 3- hydroxy- 3 - methylglutaryl - CoA lyase deficiency （HMG, 3 cases ）, and beta-keto thiolase deficiency （BKT,4 cases）. C5-OH was the only finding in the former two diseases,but in patients with BKT,senecioyl-earnitine was also elevated significantly. Only was the isovalerylcarnitine level increased in 5 cases of isovalerie acidemias. In 3 cases with glutarie aeidemia type Ⅰ ,only was glutarylearnitine increased. But in 2 cases with glutarie acidemia type Ⅱ ,variety of the aeylcarnitines was also increased. Conclusions The organic acidemias can be identified by analysis of acylcarnitines amino acids and the ratio of acylcarnitines with tandem mass spectrometry,which can also be used for differential diagnosis of various types of organic acidemias. But,in some patients with organic academia,the diagnosis should be confirmed with the organic acid analysis using urine gas-chromatography mass spectrometry.