A Natural History Study of Biomarkers and Clinical Outcomes in Mucopolysaccharidosis Type IIIA (MPS IIIA; Sanfilippo Syndrome)

Inclusion criteria

• Age of enrollment is as follows:

• All participants must be between 4 months and < 14 years at time of consent
• At least 10 participants (ie, approx. 50% of expected total population) must be between 4 months old and < 4 years old at the time of consent
• The participant has a confirmed diagnosis of Mucopolysaccharidosis Type IIIA (MPS IIIA) (i.e., Sanfilippo syndrome) based on at least 2 out of the 3 following criteria:

• Documented reduced N-sulphoglucosamine sulphohydrolase (SGSH) activity in plasma, white blood cells, and/or skin fibroblasts consistent with MPS IIIA (10% or less of the lower limit of the normal range based on the testing laboratory)
• Documented likely pathogenic variant of the SGSH gene
• Documented elevated heparan sulfate levels in urine and/or blood Participants and their families are willing to complete 7 blood draws and 7 Vineland-3 collections

Exclusion criteria

• Known history of HIV, hepatitis, or other infectious diseases
• Taken an investigational product in the last 30 days
• Experienced excess blood loss, including blood donation, defined as 80 mL in the last month or 160 mL in the previous two months
• Undergone an MPS IIIA gene therapy at any time unless prior Sponsor or designee's approval has been received
• Documented loss of activity of sulfatases other than N-sulphoglucosamine sulphohydrolase (SGSH), indicating multiple sulfatase deficiency
• Known genetic or acquired disorder associated with developmental delay, seizures or other significant CNS dysfunction that would be expected to confound the clinical or biomarker assessments