Their 15-month-old son Carmani, asleep in his crib in a nearby room, had a severe case of sickle cell anemia. In a little more than an hour, in an 8-foot-square, glass-walled room at Miami Children's Hospital, doctors would put a central line in his fluttering chest and begin preparations for an intensive round of chemotherapy in advance of a complete cord-blood stem-cell transplant. The process would involve weeks of painful treatment. If it worked, Carmani would be free of sickle cell disease. If it didn't work, if he became infected or his system rejected the transplant, he could die.