CD40LG and cold agglutinin disease: Cold-antibody autoimmune hemolytic anemia, referred to as cold agglutinin syndrome (CAS) or cold agglutinin disease (CAD), is a rare autoimmune condition characterized by the presence of high levels of cold-sensitive autoantibodies in the blood, primarily IgM, as well as autoantibodies that remain active at temperatures below 30 °C (86 °F) [3,12,20,70,71,72,73,74,75,76].