The goal of this study is to observe patients with Homocystinuria (CBSDH) over 3 years to learn how their disease is managed under regular circumstances. This study does not involve any investigational medications, but will provide information to researchers who are currently developing a medication to treat the disease. The study has 5 main parts, all of which are provided free of charge to participants: DXA exam, blood draws, ophthalmology exam, cognitive testing, and physical exams. To learn more about the study, please contact our team via the information listed below.