A novel nonsense mutation p.W738X of GAA gene identified in a Chinese patient with infantile glycogen storage disease type Ⅱ / 临床儿科杂志

ABSTRACT

Objective To investigate the acid α glucosidase(GAA)gene mutations and clinical features of a Chinese patient exhibiting signs and symptoms of infantile glycogen storage disease type Ⅱ(GSD Ⅱ). Methods Clinical features of the patient were reviewed,and GAA activity in the patient＇s and her parents＇ whole leukocytes were measured. GAA coding regions were amplified by polymerase chain reaction(PCR),and analyzed by direct DNA sequencing. Results The patient showed feeding difficulties,generalized hypotonia and weakness starting at 2 months of age. Cardiomegaly and cardiomyopathy were found at 4 months. She died of cardiorespiratory failure at the age of 6 months. GAA activity in leukocytes was low in the patient(17.3% of the median normal range). Genotyping revealed the patient was a heterozygote for a novel nonsense mutation p.W738X and a previously reported nonsense mutation p.E888X. The reported pseudodeficiency allele c.1726G ＞ A;2065G ＞ Awas found in the patient and her mother. Conclusions Correct diagnosis was made for this patient by combination of GAA activity assay and genetic analysis. From the clinical course,this patient should be classified as infantile type of GSD Ⅱ,suggesting that the novel mutation p.W738X may have a damaging effect on the function of GAA. Pseudodeficiency allele found in this family highlights the importance of genetic analysis of GAA when performing diagnosis and prenatal diagnosis for the affected families,as this allele causes low GAA activity in normal individuals.