A Natural History Study of Angelman Syndrome

The goal of this observational study is to learn about the natural progression of Angelman syndrome (AS) in children and adults with a confirmed genetic diagnosis of AS. The main questions it aims to answer are: * How do developmental skills, such as communication, motor abilities, and adaptive behaviors, change over a 1-year period in people with AS? * Are there specific patterns in brain activity or sleep that are associated with changes in AS symptoms over time? Participants will: * Attend 3 in-person and 2 virtual study visits over 1 year for assessments. * Complete tests and questionnaires about development, behaviors, and sleep with the help of their caregivers. * Undergo electroencephalograms (EEGs) to measure brain activity and wear a sleep-monitoring device at home (to collect actigraphy data).