A promising approach for the treatment of genetic diseases is called gene therapy. Gene therapy is a relatively new field of medicine that uses genetic material (mostly DNA) from the patient to treat his or her own disease. In gene therapy, the investigators introduce new genetic material in order to fix or replace a diseased gene, with the goal of curing the disease. The procedure is similar to a bone marrow transplant, in that the patient's malfunctioning blood stem cells are reduced or eliminated using chemotherapy, but it is different because instead of using a different person's (donor) blood stem cells for the transplant, the patient's own blood stem cells are given back after the new genetic material has been introduced into those cells. This approach has the advantage of eliminating any risk of Graft-Versus-Host Disease (GVHD), reducing the risk of graft rejection, and may also allow less chemotherapy to be utilized for the conditioning portion of the transplant procedure. The method used to fix or replace a diseased gene is called gene editing. A person's own cells are edited using a specialized biological medicine that has been formulated for use in human beings. Fetal hemoglobin (HbF) is a healthy, non-sickling kind of hemoglobin. Investigators have recently discovered a gene called BCL11A that is very important in the control of fetal hemoglobin expression. Increasing the expression of this gene in sickle cell patients could increase the amount of fetal hemoglobin while simultaneously reducing the amount of sickle hemoglobin in their blood, and therefore potentially cure the condition.