CRIM Status Determination and Longitudinal Follow-up in Infantile Pompe Disease

Infantile-onset Pompe disease is an inherited disorder caused by lack of or defect in the enzyme acid alpha-glucosidase (GAA). GAA enzyme deficiency causes glycogen to build up and damage cells throughout the body, especially in the heart and muscles, which is normally diagnosed within the first months of life. Current treatment for Pompe disease involves enzyme replacement therapy (ERT) using the drug alglucosidase alfa (Lumizyme/Myozyme), which provides a form of the GAA enzyme to replace the enzyme that is missing or not working properly in the patient's blood. In this study, the investigators will learn about the patient's ability to tolerate ERT. Cross-Reactive Immunological Material (CRIM) is a measurement of natural GAA production and an important factor that affects how patients respond to ERT. Children who produce some natural GAA are classified as CRIM-positive, while children who do not produce any natural GAA are classified as CRIM-negative. Children who are CRIM-positive generally tolerate ERT well. But, children who are CRIM-negative, and some children classified as CRIM-positive, have a poor response to ERT due to complications from an immune response against the drug. Treatments are currently being developed to stop this immune response and prevent complications from ERT. This is a longitudinal natural history study of Infantile Pompe disease. The investigators will regularly collect and review medical information regarding the diagnosis of Pompe disease, response to enzyme replacement (ERT) using alglucosidase alfa (Lumizyme/Myozyme) and response to immunosuppressive therapy in cases at risk for developing or those who have developed high and sustained antibodies to ERT. The specific aims of this study are: 1. To correlate CRIM status determined in a blood sample or cultured skin fibroblasts with GAA gene variants that are causing your child's Pompe disease. 2. To explore the clinical treatment response and natural history of CRIM-positive and CRIM-negative Pompe disease patients with and without immune modulation. 3. To investigate the role of immune response to treatment (IgG and IgE) including immune phenotyping.