A Study of the Safety and Pharmacokinetics of rhGAA in Siblings With Glycogen Storage Disease Type II

Inclusion Criteria: * Written informed consent must be obtained from the parent or guardian prior to performing any study related procedures; * Patient must have a clinical diagnosis of GSD-II confirmed by endogenous GAA activity below normal in at least one tissue; * Patient must have a sibling with a clinical diagnosis of GSD-II confirmed by an endogenous GAA activity below normal in at least one tissue, who is eligible for participation in this study; * Patient must have a sibling with identical GAA mutations who is eligible for participation in this study; * Patient must have a sibling with evidence of different progression of GSD-II who is eligible for participation in this study; * The patient or his/her guardian(s) must have the ability to comply with the clinical protocol. Exclusion Criteria: * Patient has significant organic disease (with the exception of symptoms relating to GSD-II), including clinically significant cardiovascular, hepatic, pulmonary, neurologic, or renal disease, or other medical condition, serious intercurrent illness, or extenuating circumstance that, would preclude participation in the trial; * Patient is participating in another investigational study.