Abstract
Autoimmune hemolytic anemia (AIHA) is caused by premature erythrocyte destruction mediated by autoantibodies (auto-Ab) with or without complement activation. The most frequent form (60%-70% of cases) is warm AIHA (wAIHA), driven by immunoglobulin G auto-Ab that react at body temperature. Cold agglutinin disease (CAD, 20%-25%) is the second most common form and is caused by immunoglobulin M auto-Ab that usually react at temperatures <20°C and strongly activate complement. Rarer forms (5%-10%) include mixed AIHAs (wAIHA plus CAD), and paroxysmal cold hemoglobinuria. Here, we present the management of wAIHA, as CAD is discussed separately. Approximately 50% of wAIHA are primary, whereas the remainder are secondary to various conditions (infections, lymphoproliferative disorders, systemic or organ-specific autoimmune diseases, congenital immunodeficiencies, hematopoietic stem-cell transplantation, and several drugs, including immune checkpoint inhibitors). The disease is highly heterogeneous, ranging from fully compensated to life-threatening, and frequently has a relapsing course. Standard first-line therapy includes steroids with or without intravenous immunoglobulin, transfusions when anemia is clinically significant, prophylactic anticoagulation for severe hemolysis, and recombinant erythropoietin when reticulocytopenia/inadequate bone marrow compensation is present. For severe cases, high-dose steroids and plasma-exchange may be considered. Rituximab is now the preferred second-line option for relapsed/refractory patients, comparing favorably with the traditional splenectomy. The latter is increasingly reserved for later lines together with classic immunosuppressants. Several novel treatments are in development for refractory wAIHA, encompassing drugs targeting B-cells (parsaclisib, ibrutinib, rilzabrutinib, zanubrutinib, obexelimab, ianalumab, povetacicept), plasma cells (bortezomib, daratumumab), spleen tyrosine kinase (fostamatinib, sovleplenib), and the neonatal Fc receptor (nipocalimab).