假肥大型进行性肌营养不良患者的基因型、表型分析及随访研究

Genotype,phenotype analysis and follow-up study on patients with Duchenne/Becker muscular dystrophy

目的:总结假肥大型进行性肌营养不良(Duchenne/Becker muscular dystrophy,DMD/BMD)患者的临床特征并进行基因诊断,分析基因型与表型的关系,以提高其诊疗水平。方法:收集整理90例患者的临床资料,提取外周血基因组DNA,采用多重连接探针扩增(multiplex ligation-dependent probe amplification,MLPA)的方法进行抗肌萎缩蛋白基因DMD突变的检测,对未检测到缺失或重复的患儿扩增其肢带型肌营养不良2I型(limb girdle muscular dystrophy,LGMD2I)致病基因FKRP的外显子,然后进行DNA直接测序,并随访患者病情变化。结果:从临床确诊的90例DMD/BMD患者中检测出58例DMD基因外显子缺失(64.44%,58/90),9例外显子重复(10.00%,9/90),检出突变的34例患儿的母亲中17例(50%,17/34)为缺失/重复的杂合性改变。对23例未检测到DMD基因重复或缺失的患儿进一步直接测序FKRP基因编码序列,未发现致病突变。对14例患儿按照国外文献方案进行小剂量泼尼松短期间歇治疗,随访发现短期内激素治疗未见明显疗效,因例数及疗程不够尚不能得出结论;其中1例患儿母亲再次怀孕后在北京大学第一医院行产前诊断,经MLPA检测羊水细胞,诊断胎儿为女性携带者。结论:本组病例显示,DMD基因缺失突变主要发生在热点区45～54外显子之间,重复突变主要发生在基因的5′端。识别DMD?BMD的临床特征及基因突变的类型有助于提高对该病的认识,判断预后。MLPA作为一种简便快速的诊断方法可对DMD?BMD进行基因诊断,检出携带者,更好的进行遗传咨询。

Objective：To improve the diagnosis and management of Duchenne/Becker muscular dystrophy（DMD/BMD）. Methods：Clinical features of 90 cases of DMD/BMD were collected. Genomic DNA was extracted using standard procedures from the peripheral blood leukocytes,and multiplex ligation-dependent probe amplification （MLPA） was applied to detect DMD gene to identify genetic mutation. For those patients whose deletion/duplication mutation was not identified,FKRP gene mutation analysis was performed using PCR-DNA direct sequence. All the cases were followed up. Results：Among the 90 cases of clinically diagnosed DMD/BMD,exons deletion of DMD was detected in 58 cases （64.44%）,and exons duplication in 9 （10.00%）. Among the 34 mothers with an affected boy but without previous genetic conformation,17 were confirmed to be carriers with gene deletion/duplication. None of the 23 cases,without detected DMD gene deletion/duplication,carried FKRP gene mutation. Fourteen children were given short-term intermittent prednisone therapy （0.75 mg/kg daily during the first 10 days of each month）. The course was not long enough and the sample size was too small to conclude any benefits or side effects. Prenatal diagnosis was provided for one mother in her next pregnancy detecting a female carrier fetus. Conclusion：DMD gene deletions mainly occurs between exons 45 and 54,while duplications mostly at 5′-terminus. Identification of the characteristics and types of gene mutation may facilitate the recognition and prognosis prediction of DMD/BMD. MLPA is a non-complex and quick diagnostic tool for DMD/BMD and its carriers,and also helpful in genetic counseling.