The purpose of this study is to find out if an investigational new drug combination called cipaglucosidase alfa/miglustat can safely help children with a rare genetic disorder called late-onset Pompe disease (LOPD).

The study drugs are provided by the Sponsor. The estimated participation time in this study is 14 months. The patient will need to receive treatment every two weeks. Patients will have blood work, exams, EKGs, lung function tests, questionnaires, muscle strength tests with physical therapy, and urine tests.