Cold agglutinin disease (CAD) is a rare autoimmune disease characterized by the presence of high concentrations of circulating cold sensitive antibodies, usually IgM and autoantibodies that are also active at temperatures below , directed against red blood cells, causing them to agglutinate and undergo lysis. It is a form of autoimmune hemolytic anemia, specifically one in which antibodies bind red blood cells only at low body temperatures, typically 28–31 °C.
