一例May-Hegglin异常家系临床及分子生物学研究

Clinical and molecular-biological study of a May-Hegglin anomaly family

目的 探讨May Hegglin异常 (MHA)患者的血小板改变及其分子遗传学特征。 方法 对先证者及其家系成员的静脉血 ,分别进行机数和镜数血小板计数 ,观察血小板形态 ,以流式细胞术分析血小板膜蛋白 ,ELISA法检测血小板膜抗体 ,用聚合酶链反应 (PCR)技术扩增先证者及其父亲非肌性肌球蛋白重链 9基因 (MYH 9)的 2 5 ,30 ,38,4 0号外显子 ,分析PCR产物的核苷酸序列 ,确定突变点 ,用间接免疫荧光结合细胞核染色技术显示粒细胞中的包涵体 (D hle小体 )。结果 患者机数血小板数明显低于镜数血小板数 ,巨大血小板占 90 %以上 ,血小板膜糖蛋白 (CD4 1、CD6 1、CD4 2a、CD4 2b)均在正常范围内 ,膜抗体未能检测到 ,血小板功能正常 ,MYH 9基因 38号外显子第 5 5 2 1位核苷酸存在G→A杂合突变 (GAG→AAG) ,从而导致其编码的非肌性肌球蛋白重链A(NMMHC A)第184 1位谷氨酸变为赖氨酸 ,正常对照及家系中正常者未见此突变 ,MHA患者中性粒细胞胞浆中荧光分布显示了“梭形”包涵体的形态和轮廓。结论 MYH 9基因点突变并伴有血小板减少和巨大血小板是MHA的主要特征。

Objective To study the changes of platelet in May-Hegglin anomaly (MHA) and the molecular pathogenesis mechanism. Methods Peripheral blood was drawn from th e MHA proband, her father and her uncle.Platelet count and morphology were exami ned by automatic blood cell counter and microscopy, respectively. The platelet membrane protein was examined by flowcytometry.Membrane antibodies were determined by ELISA. PCR was used to amplify the exons 25,31～32,38 and 40 of the MYH 9 gene in the MHA patient and her diseased father . Furthermore, PCR products were sequenced, a specific point mutation was identi fied and inclusions (Dhle's body)in the neutrophil was detected by indirect i mmunofluorescence technique. Results It was proved that in MHA pati ents, platelet count was higher by cell counter than by micoscope (P <0.01). Giant platelet was 94% but platelet membrane proteins (CD41,CD61,CD42A, CD42b) were in normal range. Membrane antibodies was undetectable. An A5521G mut ation (GAG→G) in the exon 38 was found in the proband and her diseased father , resulting in a characteristic change of NMMHC-A1841 (Glutamic acid→Arginine) , which was not found in other members of the family and in normal controls. Spi ndle-like inclusions with fluorescence were clearly displayed in neutrophil cy toplasm. Conclusion The molecular pathogenesis mechanism of May-He gglin anomaly is the mutation in MYH 9 gene.