The patient must provide signed, informed consent prior to performing any study-related procedures.

The patient must have a diagnosis of Pompe disease based upon:

The patient must be greater than 8 years of age if enrolled at a site in the U.S. and greater than 18 years of age if enrolled at a site in Europe

The patient must have documented onset of symptoms of Pompe disease after 12 months of age

The patient must have at least 3 testable muscle groups in the arms and 3 testable muscle groups in the legs using quantitative muscle testing

The patient must be able to perform pulmonary and muscle function testing in the supine position

The patient must be able to provide reproducible muscle and pulmonary function test results within 10% of each other performed on Day 1 and Day 2 of the Screening/Baseline visit and forced vital capacity measurements within 10% of each other performed in the upright position on Day 1 and Day 2 of the Screening/Baseline visit

The patient must have the ability to comply with the clinical protocol

The patient is unable to ambulate (use of assistive devices, such as walker, cane, crutches, is permitted);

The patient requires the use of invasive ventilatory support.

The patient requires the use of noninvasive ventilatory support during waking hours.

The patient has received enzyme replacement therapy with acid alpha-glucosidase from any source

The patient has received an investigational drug within 30 days prior to study enrollment, or is currently enrolled in another study which involves clinical evaluations

The patient has a medical condition, serious intercurrent illness, or other extenuating circumstance that, in the opinion of the Investigator, may significantly interfere with study compliance including all prescribed evaluations and follow-up activities

The patient has a major congenital abnormality

For female patients only, the patient is pregnant or lactating, or is unwilling to practice birth control methods during the course of the study