Pomp Disease is a genetic condition that causes muscles to weaken because the body cannot properly break down a sugar called glycogen. People with late-onset Pompe disease are being studied to understand how their bodies react to treatments and their antibody levels. Antibodies are proteins in the blood that help fight infections. This study focuses on those who have not had gene therapy using AAV (a virus used to deliver healthy genes into cells) and have been on enzyme replacement therapy for at least 6 months. Blood and urine samples will be collected to study antibodies and other substances called biomarkers, which give more information about the disease.

The study will last up to 2 years, with visits every 4 months. Participants will have medical checkups and tests during these visits. No new treatments will be given.

• Study lasts up to 2 years with visits every 4 months.
• No new treatments are given; only blood and urine tests.
• Participants must be willing to comply with study visits and not join other studies.