Inclusion Criteria:

• male or female aged greater than or equal to 18 years
• patient's legally authorized guardian(s) must provide signed, informed consent prior to initiation of study; patient's signature required if patient understands informed consent
• patient must have a documented deficit in acid alpha-glucosidase (GAA) activity , corresponding to the diagnosis of Pompe disease confirmed by documented genotyping
• patient presents with advanced documented symptoms of the disease defined as follows: patient is in a wheel chair and presents diaphragmatic dysfunction and requires invasive ventilation or non invasive ventilation (12 or more hours daily)

Exclusion Criteria:

• patient has received enzyme replacement therapy with GAA from any source
• patient has taken an experimental drug in the 30 days prior to study enrollment, or is currently included in another study involving clinical evaluations; If this is the case, inclusion of the patient in the present study will be subject to prior agreement by Genzyme
• major congenital anomaly
• clinically important organic disease (except for symptoms related to Pompe disease) or any other medical condition, serious intercurrent illness, or other extenuating circumstance that, in the physician's opinion should preclude the patient's participation in the study or may reduce survival
• pregnancy and breastfeeding (women of childbearing age must use a medically accepted method of contraception throughout the entire duration of the trial. Male patients must use a medically accepted birth control method throughout the entire duration of the study)