一个先天性肌营养不良1A型家系的临床、分子病理及遗传学研究

Clinical, molecular pathological and genetic analyses of a Chinese family with congenital muscular dystrophy type1A

目的分析并确立1个先天性肌营养不良1A型（congenital muscular dystrophy type 1A，MDC1A）家系的临床、分子病理及遗传学特征。方法收集该家系患儿及父母的临床资料，对患儿进行腓肠肌活检，采用特异抗体行免疫组织化学染色，包括merosin抗体、抗“抗肌萎缩相关糖蛋白（α—dystroglycan，α—DG）糖链抗体ⅡH6、抗β抗肌萎缩相关糖蛋白（β—dystroglycan，β—DG）抗体及抗肌萎缩蛋白（dystrophin）C末端（Dys—C）抗体；提取患儿及其父母外周血基因组DNA，PCR扩增LAMA2基因的65个外显子，以琼脂糖凝胶电泳鉴定PCR产物，PCR产物纯化后DNA直接测序，确定基因突变的类型，分析基因型和表型的关系。结果患儿自幼运动发育落后，肌病面容，肌酶中度升高，头颅MRI提示脑白质异常信号，临床诊断为先天性肌营养不良1A型。通过活检肌肉组织免疫学染色提示merosin完全缺失，dystrophin和DG表达正常。基因检测显示先证者LAMA2基因第5外显子c．817A〉T纯合突变，其父母分别为此位点杂合突变。结论本次研究进一步明确了MDC1A患儿的临床特点，通过分子遗传学分析发现该患儿为LAMA2基因c. 817A〉A（p．R273X）纯合无义突变，其突变基因分别来自父母，符合先天性肌营养不良1A型常染色体隐性遗传的规律，可确诊为先天性肌营养不良1A型。

Objective To analyze and characterize the clinical, molecular pathological and genetic features of a Chinese family with congenital muscular dystrophy type 1A （MDC1A）. Methods Clinical data of the proband and her family members were collected. Immunohistochemistry staining was performed on muscular biopsy tissues with anti-merosin, α-dystroglycan, β-dystroglycan and dystrophin antibodies. Genomic DNAs from the patient and her parents were extracted using standard procedures from the peripheral blood leukocytes. PCR and DNA direct sequencing were employed to analyze all of the 65 exons of the LAMA2 gene to determine the gene mutation, and the relationships between genotype and phenotype were analyzed. Results The proband presented with delayed motor development and a myopathic face. Her midrange elevated serum creatine kinase （CK） levels and white matter signal intensity changes are consistent with MDC1A, and was clinically diagnosed as MDC1A. The immunohistochemistry analysis for the proband exhibited complete loss of merosin staining. Further test with PCR detected a homozygous mutation of c. 817A〉T in exon 5, while her parents were heterozygotes for the mutation. Conclusion The authors have defined the clinical manifestation of the Chinese family with MDC1A. The proband carried a homozygous nonsense mutation c. 817A〉T, and her parents were heterozygous carriers, consistent with autosomal recessive inheritance.