Lumizyme (alglucosidase alfa) is an enzyme replacement therapy used to treat Pompe disease (GAA deficiency), a genetic disorder where the body lacks the enzyme needed to break down glycogen. This condition can cause muscle weakness, heart problems, and breathing issues. Lumizyme works by replacing the missing enzyme, alglucosidase alfa, to break down glycogen and help reduce the symptoms associated with the disease in both adults and children.