三个遗传性血小板无力症家系临床特性和基因分析

Analysis of clinical features and genotype in three Chinese pedigrees with Glanzmann thrombasthenia

目的对三个遗传性血小板无力症（GT）家系进行整合素αⅡbβ3临床特性分析和基因突变检测。方法经BPC、血涂片、出血时间（BT）、凝血常规检查、血小板聚集试验和流式细胞术进行实验检测；用PCR法对先证者αⅡbβ3基因所有外显子及其侧翼序列进行扩增；PCR产物纯化后直接测序，检测其基因突变。突变位点经直接测序排除基因多态性，103名健康人作对照。结果三个家系的先证者BPC正常，血小板不聚集，BT延长，凝血常规指标检查正常，对ADP、凝血酶、肾上腺素、胶原、花生四烯酸等多种诱聚剂反应低下，而对瑞斯托霉素反应基本正常；家系1和家系3先证者的血小板膜表面αⅡbβ3的含量极度降低，家系2先证者的血小板膜表面αⅡb阳性血小板为63％，β3阳性血小板为76％。家系1先证者αⅡb基因存在G10A纯合突变，β3基因存在G1412T纯合突变。家系2先证者β3基因存在G1199A和1525delC复合杂合突变。家系3先证者在αⅡbβ3基因未检测到突变。结论G10A和G1412T复合纯合突变是导致家系1先证者发生GT的原因，G1199A和1525delC复合杂合突变是导致家系2先证者发生GT的原因。G10A、G1412T和1525delC为国际首次报道的突变。

Objective To study the clinical feature and αⅡbβ3 gene mutations of three Glanzmann thrambasthenia （GT） pedigrees. Methods Platelet counts （BPC）, blood film, bleeding time, platelet aggregation and flow cytometry were used for phenotype diagnosis of all the patients. All the exons of αⅡb and β3 genes were amplified by polymerase chain reaction （PCR） and direct sequencing was performed for mutational screening. One hundred and three healthy blood donors were as normal controls. Results Three probands showed normal BPC, defective platelets aggregation, prolonged bleeding time and significantly reduced platelet aggregation to ADP, epinephrine, and collagen, while relatively normal aggregation to ristocetin. Flow cytometry showed platelet surface expressed αⅡbβ3 was strongly reduced in proband 1 and proband 3 and mildly reduced in the amount of surface expressed αⅡbβ3 （63%） in proband 2. Sequencing results showed that proband 1 had a G10A homozygous mutation in αⅡb, and a G1412T homozygous mutation in β3. Compound heterozygous mutations in β3, G1199A and 1525delC were identified in proband 2. No mutations in αⅡbβ3 gene were identified in proband 3. Conclusions Compound homozygous mutations, G10A in αⅡb and G1412T in β3, lead to GT in proband 1. Compound heterozygous mutations in β3, G1199A and 1525delC, lead to GT in proband 2. The mutations of G10A, G1412T and 1525delC were reported for the first time in GT patients.