Objectives: To explore the GAA varient spectrum and the genotype-phenotype correlations in patients with glycogen storage disease type Ⅱ (Pompe disease, PD), as well as to estimate the disease incidence based on carrier rate of GAA varients in Guangzhou population. Methods: A total of 57 PD cases were retrospectively enrolled at Guangzhou Women and Children's Medical Center from January 1, 2010 to May 31, 2020. All patients presented symptoms before the age of 18 years. Each diagnosis was further confirmed by GAA enzyme activity and GAA variants. The carrier rate of GAA varients was calculated based on variants detected by whole exon sequencing among 2 395 healthy children in Guangzhou. Results: Among the 57 PD patients (including male 26, female 31),twenty-eight patients with infantile onset PD (IOPD) presented with progressive general muscle weakness and cardiomyopathy. The mean ages of symptom onset and diagnosis were (2.5±1.4) and (5.0±3.0) months, respectively. Twenty-six cases died in the first year after birth.Twenty-three patients with late onset PD (LOPD) presented with progressive muscle weakness. Seven of them had respiratory failure at diagnosis. The mean ages of symptom onset and diagnosis were (12.0±5.0) and (17.0±7.5) years, respectively. Six children with atypical IOPD showed motor delay, muscle weakness and cardiomyopathy. Their diagnosis was confirmed at 2.5-7.0 years of age. Among the 57 patients, 47 different variants were identified in the GAA gene. Three variants: c.797C>T, c.1109G>A and c.1757C>T were novel. c.1935C>A (25/114, 21.9%) and c.2238G>C (15/114, 13.2%) were the most common variants, detected in 57.1% of IOPD and 65.2% (15/23) of LOPD patients, respectively. Among the 28 IOPD patients, 26 cases (92.9%) carried at least one missense variant which indicated positive cross-reactive immunologic material (CRIM). The carrier rate of pathogenic variants in GAA gene among healthy children was 24/2 395. The estimated incidence of PD in this population is about 1/40 000. The frequencies of pseudodeficiency variants c.1726G>A and c.2065G>A homozygotes were 26.3% (15/57) and 35.1% (20/57) in PD patients, which were significantly higher than those (1.7% (40/2 395) and 3.9% (94/2 395)) in healthy children (χ²=151.2, 121.9; both P<0.01). Conclusions: PD presents as a spectrum, some as atypical IOPD. The c.1935C>A and c.2238G>C are common variants, correlated with IOPD and LOPD respectively. The c.796C>T and c.1082C>T are usually found in atypical IOPD. The majority of IOPD patients is predicted to be CRIM positive. The estimated incidence of PD is about 1/40 000.
目的： 探讨糖原贮积病Ⅱ型患者酸性α-葡萄糖苷酶（GAA）基因变异特点及基因型与表型的关系，并根据健康儿童GAA基因变异携带率推断理论发病率。 方法： 回顾性分析2010年1月至2020年5月广州市妇女儿童医疗中心确诊的18岁前起病的57例糖原贮积病Ⅱ型患者的临床资料及GAA基因分析结果，采用荧光底物法检测外周血淋巴细胞或干血斑中GAA活性，采用Sanger测序法进行GAA基因变异分析。以2 395名健康儿童全外显子测序中GAA基因检测计算GAA基因变异携带率。组间率的比较采用χ²检验。 结果： 57例患儿中男26例，女31例。婴儿型患者28例，主要表现为进行性全身肌无力及心肌肥厚，发病年龄（2.5±1.4）月龄，确诊年龄（5.0±3.0）月龄，其中26例于1岁内死亡。晚发型患者23例，表现为肌无力、呼吸困难等，发病年龄（12.0±5.0）岁，确诊年龄（17.0±7.5）岁，7例诊断时已出现呼吸衰竭。非典型婴儿型6例，1岁左右发病，表现为肌无力伴肥厚性心肌病，诊断年龄为2.5~7.0岁。GAA基因分析显示，57例患者共检出47种变异，其中3种错义变异c.797C>T、c.1109G>A及c.1757C>T为可能致病新变异。c.1935C>A（25/114，21.9%）和c.2238G>C（15/114，13.2%）为较常见变异，57.1%（16/28）婴儿型患者检出c.1935C>A的纯合或复合杂合变异，65.2%（15/23）晚发型患者携带c.2238G>C。c.796C>T及c.1082C>T多见于非典型婴儿型。在28例婴儿型患者中，26例（92.9%）至少携带1个错义变异。健康儿童GAA基因致病变异携带率为24/2 395，推测该病的理论发病率为1/40 000。患者组GAA变异谱与健康儿童携带的GAA变异谱基本一致，假性缺陷变异c.1726G>A 和c.2065G>A 纯合子检出率在患者组分别为26.3%（15/57）和35.1%（20/57），在健康儿童组分别为1.7%（40/2 395）和3.9%（94/2 395），两组比较差异均有统计学意义（χ²=151.2、121.9，均P<0.01）。 结论： 糖原贮积病Ⅱ型临床表现呈连续的临床谱特征，少数患者为非典型婴儿型。常见的2种变异c.1935C>A和c.2238G>C分别与婴儿型及晚发型有关，c.796C>T及c.1082C>T多见于非典型婴儿型。绝大多数婴儿型患儿因携带1个错义变异推测为交叉反应性免疫物质阳性。糖原贮积病Ⅱ型理论发病率约1/40 000。.