The thalassemias refer to a diverse group of hemoglobin disorders characterized by reduced synthesis of one or more of the globin chains (a. B, gamma, gamma/delta/B, epsilon/gamma/delta/B). These are the most common disorders to cause a major public health problem worldwide. Globally it is estimated there are about 270 million carriers of hemoglobin disorders, of which 80 million are carriers of B-thalassemia.
The current conventional treatment of B-thalassemia major consists of lifelong regular blood transfusions combined with daily subcutaneous iron chelation therapy with desferrioxamine (DFO). The successful implementation of this treatment regimen improves life expectancy and quality of life. In countries where transfusions and iron chelation treatment is given irregularly, mainly due to high cost, the majority of patients with homozygous B-thalassemia die in childhood from chronic anemia and its complications and from organ iron overload.
At present, allogeneic transplant is the only treatment able to definitively cure B-thalassemia major. Results are best when the transplant is performed using an HLA identical sibling and the patient is less than 17 years of age. Although successful transplants have been performed for young adult thalassemia patients and for patients receiving unrelated donor bone marrow. The transplant conditioning regimen consists of myeloablative chemotherapy followed by bone marrow infusion. The experience using reduced intensity regimens have not been encouraging.