六例非肌性肌球蛋白重链9基因相关疾病患者的临床特征与基因分析

Clinical features and gene analyses of six patients with MYH9-related disease

目的分析6例非肌性肌球蛋白重链9（MYH9）基因相关疾病患者临床特征和基因。方法取患者外周血，光镜下计数血小板数目、涂片并瑞氏染色后观察血小板形态以及有无中性粒细胞包涵体；抽提患者外周血基因组DNA，PCR扩增MYH9基因的40个外显子及两端侧翼序列，DNA测序并与基因库序列进行比对以确定基因异常，用限制性核酸内切酶和聚丙烯酰胺凝胶电泳法分析排除多态性。结果6例患者血小板计数下降、体积增大，中性粒细胞内可见淡蓝色包涵体。基因分析发现在1号、30号和40号外显子中存在T97C（W33R）、4335InsCAGAAGAAG（1445InsQKK）、G4269A（D1424N）和G5833T（E1945Stop）4种基因突变，其中前2种突变为首次发现，并排除基因多态性的可能。结论6例MYH9相关疾病患者的基因突变中T97C（W33R）和4335InsCAGAAGAAG（1445InsQKK）是国际上首次发现的新突变。病史较长且治疗反应不佳的原发免疫性血小板减少症患者应考虑MYH9基因相关疾病的可能性。

Objective To investigate clinical features and to identify gene mutations in six patients with nonmuscle myosin heavy chain 9 gene （MYH9）-related disease. Methods The platelet counts were measured using automated complete blood cell counter and manual manner. The size of platelets and inclusion bodies were observed under light microscopy. All the 40 exons and exon-intron boundaries of MYH9 gene were amplified by PCR and then DNA sequencing was performed. Restriction endonuclease analysis and poly- acrylamide gel electrophoresis （PAGE） were used for polymorphism analysis. Results Six patients all shared the commom feasures of thrombocytopenia with giant platelets and granulocyte inclusions. Four MYH9 gene mutations were found in the six patients： T97C（W33R）in exon 1, 4335Insert CAGAAGAAG（1445IusQKK） and C,4269A（D1424N） in exon 30 and G5833T（E1945Stop） in exon 40. The former two were novel mutations which have not been reported in the literature. The results of restriction endonuclease analysis and PAGE could exclude the possibility of nucleotide polymorphisms. Conclusions The MYH9 gene mutations were identified in six patients with MYH9 related disorders, and T97C （ W33R ） and 4335InsCAGAAGAAG （1445InsQKK）were novel mutations. MYH9 related disease should be considered in individuals with persis- tent thrombocytopenia which is non-responsive to corticosteroids and immuno-repressive agents.