The purpose of this research study is to compare transplant (HCT/BMT) to standard of care treatment in young adults with SCD who have experienced complications. Once consented we would assess to see if you have a matched donor. Subjects who have a closely matched donor will undergo a bone marrow transplant. This is called the Donor Arm. Subjects who do not have a closely matched donor will receive the current standard of care for their disease. This is called the No Donor Arm. We will follow subjects in both arms for two years to evaluate outcomes over that time period.