 Participation in this observational study will be limited to current or future patients at one of the five study sites. A clinical evaluation will be performed at baseline, including a general patient history, physical and neurological examinations, a nutritional assessment, neuro-imaging, electroencephalography, laboratory testing, and neurodevelopmental testing. A blood sample or mucosal sample will also be taken at baseline to acquire DNA for potential genetic testing. All assessments except the neuro-imaging, electroencephalography, and blood sampling will be repeated at yearly study visits for as long as funding can be secured. In addition, participants will be photographed and perhaps videotaped on a yearly basis in order to document clinical phenotypes and any neurologic abnormalities. Participants may be followed-up for a total of 10 years. 