Long-term outcome in late-onset Pompe disease treated beyond 36 months (ATBIG-Pompe-Study), a multicenter, multinational, longitudinal, non-interventional observational study in subjects, at least 8 years old, diagnosed with late-onset Pompe disease retrospectively and prospectively collects data to understand clinical progression in terms of muscle and respiratory function, and clinical symptomology treated with alglucosidase alfa more than 36 months in 100 subjects.