The presentation and course of late-onset Pompe disease is much less foreseeable than the classic infantile form. Some patients experience a rapid worsening in skeletal muscle function leading to loss of ambulation and respiratory failure, while others progress less rapidly. So there is a more inconstant response to treatment in skeletal muscle and lung function in the long-term. Therefore, an unmet clinical need is the collection and analysis of long-term data of rhGAA enzyme replacement therapy (ERT) in late-onset Pompe disease patient aged 8 years and older. The principal goal of our investigator driven study is to gain conclusive insight in long-term outcome data beyond 36 months up to 10 years of ERT treatment. In addition we will collect biological samples from all patients for a future biomarker study including gene modifier search by genome and RNA seq (not part of this proposal). This study may provide clinicians and researchers with a better understanding of late-onset Pompe disease under long-term treatment, to the benefit of all patients affected with late-onset Pompe disease, as well as, individuals and families with related diseases.