Objective: To investigate the clinical and laboratory features of three children with late-onset type Ⅱ glycogen storage disease(GSD) who presented with hypertrophic cardiomyopathy and to analyze the effect of five mutations identified on the acid-α-glucosidase (GAA) activity and stability. Method: Three cases of children with muscle weakness were included in this study.GAA activity was analyzed in Dried Blood Spot of the patients.DNA was extracted from peripheral blood in all the patients and their parents and subjected to polymerase chain reaction and directly sequencing of GAA gene.Five mutant pcDNA3.1-myc-his-GAA expression plasmids(p.G478R, p.P361L, p.P266S, p.Q323X, p.R672Q) were constructed and transient instantaneously transfected into 293T cells to analyze the enzyme activity and stability of GAA. Result: All the three children had the onset of disease at 3 years or 1.5 years of age.They presented with developmental delay, muscle weakness and hypertrophic cardiomyopathy.GAA activity of 3 patients was 2.65, 3.55 and 1.51 pmol(punch·h)(8.00-98.02)respectively. Genetic analysis found 5 mutations (p.G478R, p. P361L, p. P266S, p. Q323X, p. R672Q), and all of these 3 cases had clinical manifestations and were diagnosed as late-onset type Ⅱ glycogen storage disease.Five mutant pcDNA3.1-myc-his-GAA expression plasmids were transfected into 293T cells.Five mutant enzyme activities were found to be only 9.9%-22.5% of the wild-type enzyme activity and the protein expression of the five mutants was 32.0%-63.9% compared with the wild type. Conclusion: This study reports 3 children with late-onset GSD Ⅱ accompanied by hypertrophic cardiomyopathy and compensatory stage of cardiac function in addition to limb muscle weakness.Five pathogenic mutations were identified, and these 5 mutations result in decreased GAA activity and GAA expression by in vitro functional analysis.
目的： 分析伴有肥厚性心肌病的晚发型糖原贮积症Ⅱ型的临床和基因突变特点。 方法： 对2011—2016年上海交通大学医学院附属新华医院小儿内分泌/遗传门诊就诊的3例晚发型糖原贮积症Ⅱ型患儿，分析其临床和实验室特点，干血滤纸片法检测其葡聚糖1，4－α－葡萄糖苷酶(GAA)活性，PCR产物直接测序法进行GAA基因突变的检测。对所发现的5种突变构建突变型GAA质粒，将野生型质粒与突变型质粒瞬时转染293T细胞，测定突变型及野生型GAA活性，western blot检测野生型及突变型GAA蛋白在293T细胞中的表达并进行统计学分析。 结果： 3例患儿分别在3岁或1岁6个月出现运动发育迟缓、肌无力伴肥厚性心肌病，其酸性GAA活性分别为2.65、3.55和1.51 pmol/(punch·h)(正常对照8.00～98.02)。GAA基因分析发现3例患儿携带5种致病突变(p.G478R，p.P361L，p.P266S，p.Q323X，p.R672Q)。结合临床3例患儿诊断为晚发型糖原贮积症Ⅱ型。对所发现的5种突变进行体外表达和功能研究，发现5种突变型酶活性只有野生型酶活性的9.9%～22.5%，5种突变型的蛋白表达量与野生型相比，只有野生型的32.0%～63.9%。 结论： 3例晚发型糖原贮积症Ⅱ型患儿，临床表现为四肢肌无力，均有明显的肥厚性心肌病，心功能尚处于代偿期。共发现5种GAA基因致病突变，5种突变均可导致GAA活性降低和蛋白表达量下降。.
Keywords: Acid α-glucosidase (GAA); Glycogen storage disease typeⅡ (GSD Ⅱ); Hypertrophic cardiomyopathy; Mutation.