Sickle cell disease: A transfusion at risk

Transfusion of packed red blood cells (pRBCs) is a major treatment in sickle cell disease. It replaces RBCs containing pathological hemoglobin S with healthy RBCs containing hemoglobin A, to treat or prevent vaso-occlusive crises and anemia when it is profound. Delayed hemolytic transfusion reaction (DHTR) is a life-threatening event, the frequency of which in these patients is underestimated. DHTR is essentially the consequence of anti-erythrocyte alloimmunization against donor blood group antigens. There is significant polymorphism in the expression of blood group antigens between donors of Caucasian origin and these patients, mainly of African ancestry. In the event of antigen/anti-erythrocyte antibody conflict, these patients may develop severe forms of intra-vascular hemolysis, with activation of complement up to the membrane attack complex. This is known as hyperhemolysis, as the patient's own RBCs are destroyed. Potentiation mechanisms via circulating heme are involved. The pathophysiology remains complex, as many cases develop without detectable antibodies. The diagnosis is then underestimated and should not be ruled out if the immunohematological work up is negative. Prevention is based on alloimmunization prevention, with the transfusion of compatible pRBCs for the most immunogenic systems - posing the problem of limited resources of pRBCs from donors of African ancestry - and the introduction of immunosuppressive treatments, such as rituximab. Treatment with anti-C5 convertase (eculizumab) in severe forms halts hemolysis and its deleterious effects on vascular endothelium. (c) 2024 l'Acade<acute accent>mie nationale de me<acute accent>decine. Published by Elsevier Masson SAS. All rights reserved.