5个遗传性血小板无力症家系的临床表型分析及发病机制研究

摘要

Objective To study the clinical phenotype and pathogenesy in five pedigrees of Glanzmann thrombasthenia (GT). Methods The diagnosis was based on clinical hemorrhage history, family history and laboratory tests including coagulation test, platelet aggregation test and flow cytometry. PCR amplification and direct sequencing were used to analyze all the exons and flanking sequences of α Ⅱ b and β3 gene of probands. Gene polymorphism was excluded by retrieval in SNP databases and relative literature. Results Five unrelated probands whose diagnosis was consistent with GT were evaluated. All the probands had relatively normal platelet counts and coagulation profiles, but their platelet response to ADP was impaired, and response to ristocetin was relatively normal. Flow cytometry showed that the proband 1had type Ⅲ GT, the proband 2 had type Ⅱ GT, the other three probands had type Ⅰ GT. Gene analysis revealed four mutations in α Ⅱ b gene, including 1652C ＞ T( 551Arg ＞ Gln) ,2671C ＞ T ( 891 Gln ＞ stop),2870C ＞ T(957 Ser ＞ Leu) ,2893-2897insC, and two mutations in β3 gene, including 1199G ＞ A (400Cys ＞ Tyr), 1574G ＞ A ( 525 Gly ＞ Asp). Conclusions Homozygous mutation 1199 G ＞ A of β3 gene leads to type Ⅲ GT for proband 1. Homozygous mutation 1574G ＞ A of β3 gene leads to type Ⅱ GT for proband 2. Homozygous mutation 1652C ＞ T of α Ⅱ b gene leads to type Ⅱ GT for proband 3. Homozygous mutation 2671C ＞ T of αⅡ b gene leads to type Ⅰ GT for proband 4. Compound mutation 2870C ＞ T(957Ser ＞Leu) and 2893-2897insC of α Ⅱ b gene leads to type Ⅰ GT for proband 5. Three novel mutations were identified in α Ⅱ b gene, namely 2671C ＞ T (891Gln ＞ stop) 、2870C ＞ T(957Ser ＞ Leu) and 2893-2897insC. 1574G ＞ A ( 525 Gly ＞ Asp) was identified in β3 gene for the first time internationally.%目的 对5个遗传性血小板无力症(GT)家系进行临床特征分析及基因突变检测,以探索其发病机制.方法 通过出血病史、家族史调查,止血和凝血指标检测,血小板聚集实验和流式细胞术检测血小板表面整合素αⅡbβ3表达情况明确5个GT家系的诊断,并用PCR扩增结合直接测序法分析先证者及家系成员的整合素αⅡb基因和β3基因的所有外显子及其侧翼序列,突变位点经检索SNP数据库及查找相关文献排除多态性可能.结果 5个GT家系先证者血小板计数基本正常,凝血象正常,血小板对诱导剂二磷酸腺苷(ADP)反应低下,而对诱导剂瑞斯托霉素反应基本正常;流式细胞术检测结果显示:先证者一为变异型GT,先证者二为Ⅱ型GT,其余3个先证者均为I型GT.基因分析共发现1例杂合突变及4例纯合突变:发生在αⅡb基因的4种突变分别为1652C＞T(551Arg＞Gln)、2671C＞T(891Gln＞stop)、2870C＞T(957Ser＞Leu)、2893-2897insC,发生在β3基因的2种突变分别为1199G＞A(400Cys＞Tyr)、1574G＞A(525Gly＞Asp).结论 β3 1199G＞A纯合突变是家系一先证者发生GT的原因;β3 1574G＞A纯合突变是家系二先证者发生GT的原因;αⅡb 1652C＞T纯合突变是家系三先证者发生GT的原因;αⅡb 2671C＞T(891Gln＞stop)纯合突变是家系四先证者发生GT的原因;αⅡb 2870C＞T(957Ser＞Leu)、2893-2897insC双重杂合突是家系五先证者发生GT的原因.其中2671C＞T(891Gln＞stop)、2870C＞T(957Ser＞Leu)和2893-2897insC这3种突变为首次报道发生于αⅡb基因的突变,1574G＞A(525 Gly＞Asp)为首次报道发生于β3基因的突变.