Autoimmune hemolytic anemia

Autoimmune hemolytic anemia occurs when a person's immune system produces antibodies directed against their own red blood cells. These antibodies attach to red cells, causing them to break down and reducing the number of oxygen-carrying red blood cells in circulation. Because the antibodies target common red cell antigens, they also bind to and destroy transfused red cells. Different antibody types react at different temperatures: the warm-immune type, caused by IgG antibodies, has an incidence of 5 to 10 cases per million, while cold agglutinin disease, caused by IgM antibodies, occurs in 1 to 1.8 cases per million. Some medical sources prefer the term immunohemolytic anemia to also cover drug-induced cases, though MeSH and the National Cancer Institute treat the terms as synonymous.