An Exploratory Study of the Safety and Efficacy of Prophylactic Immunomodulatory Treatment in Myozyme-naive CRIM(-)( Cross- Reactive Immunologic Material) Patients With Infantile-Onset Pompe Disease

Inclusion Criteria:

• The patient(and/or patient's legal guardian if patient is <18 years) must provide written informed consent prior to any study-related procedures that are performed.
• The patient must have a confirmed diagnosis of Pompe disease defined as documented acid α-glucosidase (GAA) enzyme deficiency from any tissue source or GAA gene mutations.
• The patient (and/or legal guardian) must have ability to comply with clinical protocol.
• The patient has not received Myozyme (alglucosidase alfa) or any other recombinant human acid α-glucosidase therapies prior to enrollment.
• The patient must be CRIM (-).

Exclusion Criteria:

• The patient has a clinical condition unrelated to Pompe disease that would interfere with program assessments.
• The patient is at risk of reactivation or is a carrier of Hepatitis B or Hepatitis C.
• The patient is at risk of reactivation or has positive serology suggestive of active infection cytomegalovirus, Herpes simplex, JC virus, parvovirus and Epstein Barr virus.
• The patient is at risk of reactivation of tuberculosis or has regular contact with individuals who are being actively treated for tuberculosis.
• The patient has a major congenital abnormality.
• The patient has used any investigational product within 30 days prior to study enrollment.
• The patient has had or is required to have any live vaccination within one month prior to enrollment.