Autoimmune hemolytic anemia (AIHA) exhibits two important characteristics: shortened red blood cell (RBC) survival and presence of autoantibodies directed toward autologous RBCs, usually demonstrated by a positive direct antiglobulin (Coombs) test (DAT). AIHA is classified by the temperature at which autoantibodies bind optimally to RBCs. In warm antibody AIHA, which constitutes about 80-90% of adult cases, hemolysis is mediated by antibodies which bind to RBCs at 37 °C (98.6 °F. In cryopathic hemolytic syndromes, cold-reactive autoantibodies exhibit affinity for RBCs optimally at temperatures below body temperature. In adults, most of the cold-reactive antibodies are agglutinins of the immunoglobulin M (IgM) isotype. In children, cold hemolysins (generally IgG) are most common. Unusual patients with mixed AIHA exhibit both cold-reactive and warm-reactive autoantibodies .