STXBP1 and SYNGAP1 Related Disorders Natural History Study

STXBP1 and SYNGAP1 related disorders are genetic disorders that cause differences in the synaptic transmission of the brain. Disease-causing variants in these genes lead to a spectrum of developmental delay that is most often severe, epileptic encephalopathies, and complex behavioral and psychiatric disorders. As there are multiple targeted therapies in development for these conditions, there is an urgent need to push forward a prospective natural history study in order to define specific disease outcomes in these genetic conditions. Participation may last up to five years and will involve up to 10 study visits. Detailed questions about health and medical history, physical exams, electrographic encephalogram (EEG) or quantitative EEG (qEEG) and some age-appropriate assessments of neurodevelopmental and behavioral function are some of the study procedures. Study procedures will occur during regularly scheduled clinic visits. Participants will undergo assessments at baseline visit and semi-annually (every 6 months for 2-5 years). The primary objective of the study is to better define and outline the clinical spectrum of STXBP1 and SYNGAP1 through detailed developmental, seizure, and quality of life assessments as an extension of routine clinical care. The secondary objectives of the study are listed below: * To evaluate changes in neurodevelopmental and behavioral parameters as assessed by instruments appropriate to the study population. * To assess the burden of disease by quality-of-life instruments appropriate to the study population. * To assess the burden of performing multiple outcome measures and scales on the caregiver, participant, and clinical personnel. * To assess health care resource utilization