[Transfusion in patients with hemoglobinopathies].

A-Thalassemia involves a production deficiency concerning the synthesis of alpha-globin chains, and beta-thalassemia involves the beta-globin chains. Only a few patients in France are affected by the major form of thalassemia (certain types of homozygotic beta-thalassemia). Also, the systematic screening of 'at-risk' couples and prenatal diagnosis has helped to considerably reduce the incidence of new cases. The decision to perform regular blood transfusions is made when Hb levels fall below values that are compatible with normal activity. Hb levels above 10 g/dL permit normal educational, recreational and professional activity. This level is generally maintained via a 15 mL/kg erythrocyte concentrate supplement every three weeks, or 20 mL/kg every four weeks. However, the appearance of antierythrocytic autoantibodies is possible, and this may also result in an increase in blood transfusion requirements. In intermediate thalassemia patients, residual Hb levels are maintained at between 7 and 10 g/dL, and transfusion of erythrocyte concentrates is only made in the case of aggravation of chronic anemia or when there are signs of intolerance to chronic anemia. In France, there is relatively large population of patients with sickle cell disease. Blood transfusion is a major element in the treatment of these patients. Simple transfusion is performed in cases of a lack of iron or folates, increased hemolysis, splenic sequestration or parvovirus 19 infection. The target hematocrit should mostly remain at the patient's baseline value. Exchange transfusions are not performed on a regular basis, but only in cases of stroke or other severe vaso-occlusive events, or when a patient has to be prepared for surgery. A minority of subjects are involved in chronic blood transfusion, which is used mostly to prevent cerebrovascular accidents but also in cases of cardiac, renal, or respiratory insufficiency. There is an increased prevalence of antierythrocytic alloimmunization in sickle cell patients, most probably because of the discrepancies in red cell antigens between mainly Caucasian blood donors and Afro-Caribbean recipients.