GSTM1 and Tangier disease: While exchange transfusion is the preferable method in condition with an emergent need to decrease HbS concentration, in higher pretransfusion Hb (˃9.0 g/dL), and for chronic transfusion with increased risk of iron overload, but this method is technically demanding, and it requires special equipment, trained personnel, adequate blood supply, and usually a central venous access [7].