<qa>  What is the name of the type of enzyme that is used by the bodys cells toGSD-II also known as Pompe disease is caused by a deficiency of a critical enzyme in the body called acid alpha-glucosidase GAA. Normally, GAA is used by the bodys cells to break down glycogen a stored form of sugar within specialized structures called lysosomes. In patients with GSD-II, an excessive amount of glycogen accumulates and is stored in various tissues, especially heart and skeletal muscle, which prevents their normal function. This study is being conducted to evaluate the safety, pharmacokinetics, pharmacodynamics and efficacy of recombinant human acid alpha-glucosidase rhGAA as a potential enzyme replacement therapy for a pair of siblings with GSD-II. To be eligible for this study, a patient must have a confirmed diagnosis of GSD-II and have a sister or brother who also has a confirmed diagnosis of GSD-II. 