Autoimmune hemolytic anemia is characterized by shortened red blood cell survival and a positive Coombs test. The responsible autoantibodies may be either warm reactive or cold reactive. The rate of hemolysis and the severity of the anemia may vary from mild to severe and life-threatening. Diagnosis is made in the laboratory by the findings of anemia, reticulocytosis, a positive Coombs test, and specific serologic tests. The prognosis is generally good but renal failure and death sometimes occur, especially in cases mediated by drugs.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 IgM isotype. In children, cold hemolysins (generally IgG) are most common. Unusual patients with mixed AIHA exhibit both cold-reactive and warm-reactive autoantibodies