As Edward Donnell Ivy remembers it, many of the sickle cell episodes he endured in his 20s were akin to headaches or colds: They hurt, but he could still get up and go. Every so often, though, he would be gripped by pain that left him unable to function. “I can’t go out the house. I can’t leave the bed,” he recalled. Then a college student, he would often wind up in the emergency room and miss weeks of classes at a time. The disease was taking a toll.