婴儿型糖原累积病Ⅱ型一家系的临床和基因突变分析

Clinical characteristics and gene mutation analysis of one pedigree with infantile glycogen storage disease type II

摘要:

收集一个家系中两例婴儿型糖原累积病Ⅱ型(GSD Ⅱ)患儿的临床资料,采用干血片法(DBS)收集患儿外周血标本并检测患儿白细胞酸性α-葡萄糖苷酶(GAA)活性;采用聚合酶链反应(PCR)对该家系GAA基因的编码区进行扩增,直接测序分析GAA基因突变情况。两例患儿为双胞胎,于10个月大时因喂养困难、全身肌肉无力、心脏增大、心功能不全就诊;两个患儿外周血GAA活性均明显低于正常;基因测序分析发现患儿存在2个复合杂合突变,分别为G1942A和G2214A,前者已经被证实具有致病性,后者是一个无义突变,导致GAA蛋白的第738位的色氨酸变成了终止密码。两患儿经基因检测明确诊断为糖原累积症Ⅱ型,未能给予酶替换治疗,随访结果,两患儿分别于15个月和17个月时死于家中。糖原累积病Ⅱ型是由GAA基因突变引起的GAA活性降低所致,DBS法检测外周血GAA活性及GAA基因检测是可行、有效的诊断方法。

Abstract:

The clinical data of 2 infants with infantile glycogen storage disease type II (GSD II) from one pedigree were collected. The method of dried blood spots (DBS) was applied to collect peripheral blood samples, and the activity of acid alpha-D-glucosidase (GAA) in leukocytes was measured. The coding region of GAA gene in this pedigree was amplified by polymerase chain reaction and then direct sequencing was used to analyze mutations in GAA gene. The two infants were twins, who were admitted to the hospital due to feeding difficulties, generalized muscle weakness and hypotonia, cardiomegaly, and cardiac insufficiency when they were 10 months old. The GAA activity in leukocytes in the two infants was significantly lower than in normal controls. Gene sequencing revealed 2 compound heterozygous mutations in the two infants, i.e., G1942A and G2214A, respectively. G1942A had been proved pathogenic, and the latter one, G2214A, was a nonsense mutation, resulting in the change of tryptophan, the 738th amino acid of GAA, into a stop codon. The two infants were diagnosed with GSD II by gene detection and no enzyme replacement therapy could be provided to them. Follow-up visits showed that the two infants died at home at the age of 15 months and 17 months, respectively. GSD II is caused by deficiency of GAA activity resulting from mutation of GAA gene. The detection of GAA activity in peripheral blood by DBS and GAA gene detection are effective and feasible methods for diagnosis of GSD II.