Cold agglutinin disease (CAD)

A form of autoimmune hemolytic anemia (AIHA) in which cold agglutinins ( autoantibodies -typically immunoglobulin M (IgM), only occasionally IgG- that react with antigens on red blood cells (RBCs) at temperatures below normal core body temperature, causing extravascular hemolysis.
Primary CAD is without any underlying disorder, secondary CAD can occur in the setting of an underlying viral infection, autoimmune disorder, or lymphoid malignancy.