Glycogen storage disease type II (Pompe disease) is caused by deficiency of the lysosomal enzyme acid α-glucosidase (GAA). The major clinical signs and symptoms are cardiomyopathy and impairment of muscle contractility. The study aimed at early diagnosis of Pompe disease among Egyptian infants, and hence the proper intervention using enzyme replacement therapy for such patients.
Patients and methods
The study included 18 patients who were suspected to have Pompe disease based on their clinical pictures. Their ages ranged from 2 months to 13 years. Positive consanguinity was present in 12 cases. Ten participants were involved as controls. GAA enzyme activity was measured in two cell types, isolated lymphocytes and mixed leukocytes. Plasma glycogen content, serum creatine phosphokinase, and lactate dehydrogenase were measured.
The activity of GAA enzyme was reduced to 3.7% in four patients and to 8.6% in controls in isolated lymphocytes and mixed leukocytes, respectively (sensitivity of both tests=1). The mean glycogen content in plasma of those four patients was 0.034±0.02 μg/µl, whereas its mean in controls was 0.57±0.12 μg/µl (P=0.0001). Patients with deficient GAA enzyme showed elevated serum creatine phosphokinase and lactate dehydrogenase levels.
The measurement of GAA enzyme activity in isolated lymphocytes and mixed leukocytes could be used as a diagnostic marker for Pompe disease. Nevertheless, GAA activity in lymphocytes was significantly lower in comparison with leukocytes for the same patients.