Pathophysiology of Acute Pain in Patients With Sickle Cell Disease

Background: Sickle Cell Disease (SCD) is a blood disorder that occurs mainly in people of African descent. Researchers want to learn more about the painful attacks and complications associated with SCD. They want to look for a relationship between SCD and specific changes in the blood. They want to study the role of genetics, inflammation, and blood clotting factors in SCD. They will do this with blood samples collected during an acute painful attack and in between attacks. Objective: To learn more about the painful attacks and complications associated with SCD. Eligibility: People ages 18-80 with SCD or who are healthy Africans or African Americans without SCD Design: * Participants will be screened with medical history and physical exam. * Healthy participants will have one visit. * Participants with SCD will have their first visit when they are not having a pain attack. They will have their next visit during a pain attack. About 3-4 months after this attack, they will have a final visit. * Visits will include a physical exam, and blood and urine tests. * Participants may have their blood samples used for genetic testing for research.