Stem Cell Transplant w/Laronidase for Hurler

Subjects will receive laronidase once a week intravenously for 10-12 weeks prior to
transplant and for approximately 8 weeks after transplant. Laronidase will be given by
intravenous infusion (IV) through a catheter and from there to your child's body's cells and
organs to break down the glycosaminoglycans (GAG) buildup.

Prior to starting ERT, subjects will have a complete physical examination, which includes a
complete assessment of your child's airway and lungs. In addition to standard treatment
evaluations and tests, which are done prior to hematopoietic stem cell transplant (HSCT),
subjects will have the following tests: an additional teaspoon of blood for a baseline test
for serum antibodies against laronidase, before and after the fourth dose of laronidase, the
investigators will collect 2 teaspoons of blood for an alpha-L-iduronidase enzyme level; to
watch for side effects to laronidase and the development of antibodies to laronidase,
approximately 2 teaspoons of blood will be collected every 3 weeks while the subject is
receiving laronidase ERT.

Inclusion Criteria:

- Patients with the diagnosis of mucopolysaccharidosis type IH (MPS I, Hurler syndrome)
who are candidates for first hematopoietic stem cell transplant (HSCT) according to a
University of Minnesota myeloablative HSCT protocol.

Exclusion Criteria:

- Not being considered for University of Minnesota myeloablative HSCT protocol.

- Previous administration of laronidase enzyme

- Second or subsequent HSCT.