Observational Study to Characterize Biomarkers and Disease Progression in Participants With Methyl CpG Binding Protein 2 (MECP2) Duplication Syndrome

The purpose of the study is to prospectively assess longitudinal changes in biomarkers (MECP2, potential biomarkers of target engagement and disease activity) in cerebrospinal fluid (CSF) and blood; characterize longitudinal changes in performance on clinical scales (clinician-reported measures of neurodevelopment and functioning) and caregiver-reported outcome assessments (communication, gastrointestinal, social-emotional-adaptive behavioral measures); evaluate longitudinal changes in caregiver-reported health-related quality-of-life measures; and assess the frequency, type, and severity of seizures over time.