This study is about understanding sickle cell disease (SCD), a blood disorder that can cause pain and damage to organs. Researchers want to learn more about how SCD affects the body over time and how treatments like hydroxyurea (HU), a medicine that helps make blood cells healthier, can help. They will collect information about SCD patients from birth until later in life to see how their health changes and what factors might help or hurt their health. Participants will have regular check-ups, which might include blood tests and other health evaluations. **Key Points:** - **Length of Study:** Participation can last from birth to over 25 years, with regular check-ups. - **Visits & Evaluations:** Include clinic visits, developmental checks, and quality of life assessments. - **Risks & Benefits:** Understanding long-term impacts of treatments and finding better therapies. This study aims to help doctors better treat SCD and improve patient care over time. Participants will help by providing valuable data on how SCD progresses and how treatments affect them.