Screening Protocol to Evaluate Acid Alpha-Glucosidase (GAA) Activity and GAA Gene Mutations in Patients With Late Onset Pompe Disease

Inclusion Criteria: * Must provide written informed consent prior to any study-related procedures being performed * Clinical presentation consistent with late-onset Pompe disease, or a current clinical diagnosis of late-onset Pompe disease * Must be greater than or equal to 8 years of age * Must be able to ambulate (use of assistive devices, such as a walker, cane or crutches, is permitted) Exclusion Criteria: * Requires the use of invasive ventilatory support * Requires the use of noninvasive ventilatory support while awake and in an upright position * Use of any investigational product within 30 days prior to study enrollment * Unwillingness to comply with protocol requirements * Has clinically significant organic disease, unstable medical condition, serious or intercurrent illness * Is pregnant or lactating * Has participated in the Prospective Observational Study in Patients with Late-Onset Pompe Disease (AGLU02303, "LOPOS")