Natural History Study of Children With Metachromatic Leukodystrophy

Inclusion Criteria: 1. Confirmed diagnosis of MLD by both: * arylsulfatase A (ASA) deficiency by assay in leukocytes AND * elevated sulfatide in urine 2. Appearance of the first symptoms of disease at or before 30 months of age. 3. A GMFM-88 total (percent) score greater than or equal to 40 at the screening examination. 4. The patient is less than 12 years of age at the time of enrollment. 5. The patient and his/her parent or legally authorized representative(s) must have the ability to comply with the clinical protocol. 6. Patient's parent or legally authorized representative(s) must provide written informed consent prior to performing any study-related activities. Study-related activities are any procedures that would not have been performed during normal management of the patient. Exclusion Criteria: 1. History of hematopoietic stem cell transplantation. 2. The patient has any known or suspected hypersensitivity to agents used for anesthesia or is thought to be at an unacceptably high risk for associated potential complications of airway compromise or other conditions. 3. Any other medical condition, serious intercurrent illness, or extenuating circumstance that, in the opinion of the Investigator, would preclude participation in the study. 4. The patient is enrolled in another clinical study that involves the use of any investigational product (drug or device) within 30 days prior to study enrollment or at any time during the study.