抗肌萎缩蛋白病一家系的临床、分子病理及遗传学特点

Clinical, molecular pathological and genetic analysis of a Chinese family with dystrophinopathy

目的分析并确定1个抗肌萎缩蛋白病（dystrophinopathy）家系的临床、分子病理及遗传学特征。方法收集先证者及其家系成员的临床资料，对先证者行肌肉活体组织检查，采用抗层黏连蛋白α2（laminin α2，又称merosin）、抗emerin蛋白、抗肌萎缩蛋白（dystrophin）中央棒状区（Dys1）、C′末端（Dys2）、N′末端（Dys3）单克隆抗体行免疫组织化学染色；提取外周血基因组DNA，采用多重连接探针扩增（MLPA）进行抗肌萎缩蛋白Duchenne型肌营养不良（DMD）基因检测。结果该家系中包括先证者在内共有3例患者临床诊断为肌营养不良，均无腓肠肌肥大，但病情重、进展较快，同时先证者肌肉活体组织检查行免疫组织化学染色提示dystrophin蛋白部分缺失，merosin、emerin染色呈阳性表达。MLPA检测显示先证者DMD基因第45-54外显子缺失，其母在第45～54外显子区域为杂合性缺失。结论该家系中的先证者DMD基因为第45-54外显子缺失，突变基因来自母亲，其母为表型正常的携带者。dystrophin蛋白表达异常是造成抗肌萎缩蛋白病表型的病理基础，其临床后果不仅取决于dystrophin蛋白表达缺失的程度，还取决于DMD基因缺失区域的功能。

Objective To analyze and determine the clinical, molecular pathology and genetic features of a Chinese family with dystrophinopathy. Methods Clinical data of the proband and his family members were collected. Immunohistochemistry staining was performed on muscular biopsy tissues with antimerosin, emerin and the N, C and central rod domains of dystrophin. Genomic DNA was extracted using standard procedures from the peripheral blood leukocytes. Multiplex ligation-dependent probe amplification （MLPA） was used to test Duchenne muscular dystrophy （DMD） gene to determine the ways and sites of genetic mutation, and analyze the relationships between genotype and phenotype. Results Patients from this family were clinically diagnosed as muscular dystrophy, and they presented serious manifestations although the immunohistochemistry analysis for the proband exhibited partial loss of dystrophin staining, and positive expression with merosin and emerin. Further test with MLPA detected the loss of exons 45--54 in DMD gene in the proband, while his mother had heterozygositic loss in exons 45--54. Conclusions The losses of exons 45--54 in the proband are all derived from his mother, who carries genetic mutation with normal phenotype. He has been diagnosed as dystrophinopathy. At the same time, his partial loss of dystrophin is not parallel to the out-of-frame mutation of the gene and his severe clinical manifestations. Abnormal expression of dystrophin is the pathological basis for dystrophinopathy phenotype. Its clinical outcome depends not only on the degree of the protein expression, but also on the function of the sites where the DMD gene loss occurs.