Observational Study to Evaluate Neurodevelopmental Status in Pediatric Patients With Hunter Syndrome (MPS II)

Inclusion Criteria: Patients must meet all of the following criteria to be considered eligible for enrollment: 1. a. The patient has a deficiency in iduronate-2-sulfatase enzyme activity AND b. The patient has a documented mutation in the iduronate-2-sulfatase gene. OR c. The patient has a normal enzyme activity level of one other sulfatase 2. The patient is male, and is at least 2 years of age and less than 18 years of age at the time of informed consent. 3. The patient must have sufficient auditory capacity at enrollment, with or without hearing aids, in the Investigator's judgment to complete the required protocol testing, and be compliant with wearing the aids on scheduled study visits. 4. The patient, patient's parent(s), or legally authorized guardian(s) has voluntarily signed an Institutional Review Board / Independent Ethics Committee-approved informed consent and/or assent form(s), as applicable. Exclusion Criteria: Patients who meet any of the following criteria will be excluded from the study. 1. The patient has clinically significant non-Hunter syndrome-related CNS involvement or medical or psychiatric comorbidity(ies) which, in the investigator's judgment, may interfere with the accurate administration and interpretation of protocol assessments, affect study data, or confound the integrity of study results. 2. The patient has a general conceptual ability score (GCA) or a developmental quotient on the cognitive scale below 55 at Screening. 3. The patient is participating in an interventional clinical trial or has participated in an interventional clinical trial within 30 days prior to enrollment; participation in non interventional observational studies is permitted.