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.