This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Hypothesis: The Administration of Myozyme Infusions will elicit significantly marked improvements in Pompe patients overall condition. The objective of the Myozyme Temporary Access Program is to provide adult patients with Pompe disease in the United States (US) access to Myozyme produced from a scaled-up manufacturing process for a limited time until production at this scale is approved for commercial use by the Food and Drug Administration (FDA). Myozyme produced via this scaled-up process has been used in other clinical studies to date, including the ongoing clinical trial in patients with late-onset Pompe disease (AGLU02704) and by all commercial patients outside the US. As is often the case with recombinant protein manufacture, the process was developed at a smaller volume, optimized, and subsequently scaled-up to produce larger volumes. Genzyme is pursuing licensure of product produced from the scaled-up manufacturing process via a supplement to the existing Biologics License Application for Myozyme. All patients will receive Myozyme at a dose of 20 mg/kg administered intravenously (IV) once every other week according to the full prescribing information for Myozyme. The total amount of Myozyme administered may be adjusted as needed to account for changes in body weight. In addition, the treating physician has the discretion to dose by ideal weight, as well as to lower the dosage during the course of the program. Safety and efficacy assessments will be performed in accordance with the Required Schedule of Assessments. An independent Data Safety Monitoring Board (DSMB) and an independent Allergic Reaction Review Board (ARRB) will review safety information. Data on screening assessments will be collected and recorded: patient demographics, medical history, including diagnosis and clinical signs and symptoms of Pompe disease, and screening urine pregnancy testing for women of childbearing potential. The occurrence of all adverse events from the time of first infusion under this program, including non-serious AE's, serious AE's and infusion associated reactions as well as any pre-treatment medications prior to infusion and concomitant medications at the time of an AE will be recorded. Anti-recombinant human acid ?-glucosidase (rhGAA) immunoglobulin G (IgG) antibody titers (prior to first infusion under this program, every 3 months, and at a patient's completion of the program) and any specialty immunologic testing performed following recurrent or moderate to severe IAR's will be recorded. The number and interval of all Myozyme infusions will be documented, noting any missed, partial, or interrupted infusions, the reasons therefore, and medications or other medical measures used to treat infusion-related reactions. Ventilator use, including any new invasive ventilator use or changes in hours of use per day, will be recorded via patient diary and entered in to the database. Motor assessments, performed using the Pompe Pediatric Evaluation and Disability Inventory (PEDI) prior to the first infusion under this program, every 6 months thereafter, and at a patient's completion of the program, will be documented. Beyond the required assessments, participating physicians will determine the frequency of additional assessments according to their patients individualized needs for medical care and routine follow-up.