Abstract
The β thalassemias are one of a few medical conditions in which reactivation of a gene product that is expressed during fetal life can functionally replace a deficiency of essential proteins expressed at a later developmental stage. The fetal globin genes are present and normally integrated in hematopoietic stem cells, and at least one fetal gene appears accessible for reactivation, particularly in β° thalassemia. However, rapid cellular apoptosis from α globin chain precipitation, and relatively low levels of endogenous erythropoietin (EPO) in some β+ thalassemia patients contribute to the anemia in β thalassemia syndromes.