The primary aim of this nationwide, explorative, cross-sectional study in Germany is to characterize the prevalence, severity and quality of musculoskeletal pain in adult patients with late-onset Pompe disease (LOPD). The secondary objectives are to evaluate whether muscle pain is associated with muscle function, to assess whether muscle pain is associated with alterations of muscle tissue, and whether vitamin D metabolism and polymorphisms of ACE and ACTN3 genes may contribute to an increased level of perceived musculoskeletal pain. In a second step, exome sequencing of genes associated with musculoskeletal pain will be analyzed. Results of LOPD patients will be compared to patients with neuromuscular disorders with a similar distribution of muscle weakness and/or musculoskeletal pain.