Rocket Study: A Study to Characterize Biomarkers and Disease Progression in Participants With Pelizaeus-Merzbacher Disease

Inclusion Criteria:

1. Participant has a parent or caregiver capable of providing informed consent (signedand dated) and able to attend all scheduled study visits and provide feedbackregarding the participant's symptoms and performance as described in the protocoland be able to comply with all study requirements

2. Participant has a diagnosis of Pelizaeus-Merzbacher Disease with geneticconfirmation of PLP1 duplication

3. Male, 6 months-17 years old, inclusive, at the time of informed consent andphenotype consistent with classic PMD

4. No contraindications for lumbar punctures (LPs), blood draws, neuroimaging, sedation (if necessary) or other study procedures

Exclusion Criteria:

1. Clinically significant abnormalities in medical history or physical examination

2. > 2 copies of the PLP1 gene

3. Have any other conditions, which, in the opinion of the investigator would make theparticipant unsuitable for inclusion, or could interfere with the participant takingpart in or completing the study