Warm autoimmune hemolytic anemia: recent progress in understanding the immunobiology and the treatment

Abstract

Autoimmune hemolytic anemia (AIHA) is defined as a condition associated with the increased destruction of red blood cells (RBCs) associated with the presence of IgG anti-RBC autoantibodies. The etiology underlying the pathogenesis of such autoantibodies is still uncertain. In the present article, we will discuss the postulated mechanisms that produce a breakdown of immunologic tolerance leading to warm AIHA including the possible roles of RBC autoantigens and the complement system, the lack of effective presentation of autoantigens, functional abnormalities of B and T cells resulting in polyclonal lymphocyte activation and alteration of cytokine production, and the role of immunoregulatory T cells. Because warm AIHA is a relatively rare clinical entity, current recommended therapeutic strategies for patients with warm AIHA are mainly based on results from small cohort studies. Clinicians must also balance the risk of withholding RBC transfusions against the possible benefit of ameliorating the hemoglobin level with such transfusions particularly in critically ill patients with warm AIHA. Glucocorticoids are the first-line treatment for patients with warm AIHA resulting in an 80% clinical response after 3 weeks of treatment. The latter, however, also may cause adverse events such as excessive weight gain, neuropsychiatric disorders, endocrine, or cardiovascular events. Splenectomy should be considered for patients who do not show a satisfactory response to glucocorticoids and may offer a success rate of up to 70% in patients with idiopathic warm AIHA. Rituximab treatment in patients with refractory warm AIHA has been well tolerated with an overall median response rate of approximately 60%. Danazol, intravenous immunoglobulin, alemtuzumab, as well as other immunosuppressive drugs have also been successfully used in patients with warm AIHA, refractory to glucocorticoids, splenectomy, and rituximab.