Background: An atypical form of life-threatening hemolytic transfusion reaction (HTR) in patients with sickle cell disease (SCD) has been well described in the literature. Continuation of blood transfusion may be lethal, as it can further exacerbate hemolysis. The pathophysiologic mechanism of HTR is not well understood.
Case reports: Two cases of severe HTR in SCD after the transfusion of compatible RBC units are reported. Hemolysis of both autologous and transfused cells was documented in Case 1 by urine Hb high-performance liquid chromotography. Multispecific HLA antibodies were identified in Case 1. Reticulocytopenia was noted in both cases during the acute hemolytic process. This was followed by a rise in reticulocyte count during receipt of IVIG and steroid therapy. Bone marrow examination during reticulocytopenia in Case 2 showed erythroid hyperplasia.
Conclusion: In SCD, both mature sickle cells and sickle reticulocytes adhere more readily to macrophages. In view of the bone marrow aspiration results, it appears that the recipients' HbS cells are destroyed by hyperactive macrophages and that the reticulocytopenia observed during HTR is likely to be due to peripheral consumption (i.e., destruction by macrophages), rather than suppression of erythropoiesis. Cessation of hemolysis during IVIG and steroid treatment may be due to IVIG's blocking of the adhesion of sickle cells and reticulocytes to macrophages, together with steroid suppression of macrophage activity.