目的·探讨成年晚发型糖原贮积症Ⅱ型（glycogen storage disease type Ⅱ，GSD Ⅱ）先证者及家系的临床和基因突变特点。方法·分析1例成年晚发型GSD Ⅱ型先证者的临床资料并追踪其家族史，分析肌肉核磁共振（magnetic resonance imaging，MRI）及肌肉病理特点。提取先证者及其父亲外周血DNA，进行基因检测分析。结果·先证者表现为渐进性肌无力7年，活动后气喘2年。父母为近亲婚配（表兄妹），家系5代18名成员中仅先证者1名存在临床表型。患者肌酸激酶中度升高，双下肢肌肉MRI显示肌肉萎缩严重，脂肪成分增多。肌肉活检病理提示肌肉空泡样变性，酸性磷酸酶活性增高。基因测序确定先证者致病突变为酸性α-葡萄糖苷酶（acid α-glucosidase，GAA）基因c.1634C>T纯合突变，其父亲为c.1634C>T杂合突变。结论·GAA基因c.1634C>T纯合突变可导致晚发型GSD Ⅱ型。

Objective · To investigate the clinical and genetic characteristics of adult late-onset glycogen storage disease type Ⅱ (GSD Ⅱ). Methods · The clinical data, muscular magnetic resonance imaging (MRI) and muscle pathological characteristics of a patient with late-onset GSD Ⅱ were retrospectively analyzed and his family history was investigated. Peripheral blood DNAs of the proband and his father were extracted for genetic testing. Results · The proband presented progressive limb weakness for 7 years and short of breath after activities for 2 years. His parents were inbred, but he was the only one among the 18 members of 5 generations who had clinical phenotype. The blood creatine kinase moderately increased. The muscle MRI of both lower limbs showed that muscles were severely atrophied, and the fat component increased significantly. The pathological findings of muscle biopsy indicated vacuolar degeneration and increased activity of acid phosphatase. Gene sequencing confirmed that the pathogenicity was a homozygous mutation of acid α-glucosidase (GAA) gene c.1634C>T, and his father was a heterozygous mutation of c.1634C>T. Conclusion · Homozygous mutations of GAA gene c.1634C>T may lead to late-onset GSD Ⅱ .