Study About the Evolution of Severe Late Onset Pompe Disease Patient With Pulmonary Dysfunction and Receiving Myozyme®

Inclusion Criteria: * Male or Female ≥ 18 years of age; * The patient and/or patient's legal representative has given their informed consent in writing before any study procedure is initiated; * Pompe disease confirmed by documented deficit in endogenous acid alpha-glucosidase (GAA) activity; * A severe form of the disease as defined as follows: a. Moderate to severe limb girdle muscle weakness requiring help for walking around (sticks, crutches, walking frame or wheelchair); and b. Symptoms of diaphragmatic dysfunction defined by at least 2 out of the 3 following criteria: orthopnea, vital capacity \< 50%, paradoxical respiration detected in measurement of transdiaphragmatic pressure; and c. Use of invasive ventilation (defined by need for tracheotomy) or noninvasive ventilation (defined by utilization of assisted ventilation using a nasal or facial mask)day and night prescribed ≥ 12 hours/day; * Treated for ≥6 months with Myozyme; * Followed-up in a reference center according to the CETP recommendations. Exclusion Criteria: * The patient presents with a major congenital anomaly; * The patient presents with a clinically important organic disease (except for symptoms related to Pompe disease) such as cardiovascular, hepatic, pulmonary, neurological or renal disease or any other medical condition, serious disease or particular circumstances that in the investigator's opinion, should preclude the patient's participation.