A Study of Potential Treatment-Responsive Biomarkers and Clinical Outcomes in Hunter Syndrome

Key Inclusion Criteria (Part 1): * Participants aged 2 through 10 years * nMPS II subgroup: participants with a development quotient (DQ) \<85 and/or a decline of at least 7.5 points in DQ, assessed at least 6 months apart, or with the same genetic mutation as a blood relative with confirmed nMPS II Key Inclusion Criteria (Part 2): * Participants aged 2 through 30 years * nMPS II subgroup: patients with an age-adjusted DQ \<85 and/or a decline of 10 points or more in DQ in the previous 6 months or more, or with the same genetic mutation as a blood relative with confirmed nMPS II * Scheduled to undergo general anesthesia or CSF sampling for non-study-related medical reasons and parent(s)/legally authorized representative consent to donate CSF for research purposes during that procedure, or an adult patient is able to provide consent and agrees to participation in the study for CSF collection/donation Key Inclusion Criteria (Part 3): * nMPS II participants aged \<8 years Key Inclusion Criteria (Part 4): * nnMPS II participants aged 6 to 17 years Key Inclusion Criteria (Part 5): * Participants aged ≤ 3 years * Have undetermined MPS II phenotype * Do not have a large deletion(s) or rearrangement(s) in the IDS gene or other definitive mutation indicative of nMPS II * Do not have a DQ \< 85 at the screening/baseline neurocognitive assessment and/or a documented decline of at least 7.5 points in DQ in the previous 6 to 18 months * Do not have the same IDS gene varian…