Autoimmune hemolytic anemia

Autoimmune hemolytic anemia (AIHA) occurs when antibodies directed against the person's own red blood cells (RBCs) cause them to burst (lyse), leading to an insufficient number of oxygen-carrying red blood cells in the circulation. The lifetime of the RBCs is reduced from the normal 100–120 days to just a few days in serious cases. The intracellular components of the RBCs are released into the circulating blood and into tissues, leading to some of the characteristic symptoms of this condition. The antibodies are usually directed against high-incidence antigens, therefore they also commonly act on allogenic RBCs (RBCs originating from outside the person themselves, e.g. in the case of a blood transfusion). AIHA is a relatively rare condition, affecting one to three people per 100,000 per year. Autoimmune hemolysis might be a precursor of later onset systemic lupus erythematosus.Spherocytes are found in immunologically-mediated hemolytic anemias.The causes of AIHA are poorly understood. The disease may be primary, or secondary to another underlying illness. The primary illness is idiopathic (the two terms used synonymously). Idiopathic AIHA accounts for approximately 50% of cases.AIHA can be caused by a number of different classes of antibody, with IgG and IgM antibodies being the main causative classes. Depending on which is involved, the pathology will differ. IgG is not very effective at activating complement and effectively binds the Fc receptor (FcR) of phagocytic cells, AIHA involving IgG is generally characterized by phagocytosis of RBCs. IgM is a potent activator of the classical complement pathway, thus, AIHA involving IgM is characterized by complement mediated lysis of RBCs. IgM also leads to phagocytosis of RBCs however, because phagocytic cells have receptors for the bound complement (rather than FcRs as in IgG AIHA). In general, IgG AIHA takes place in the spleen, whereas IgM AIHA takes place in Kupffer cells – phagocytic cells of the liver. Phagocytic AIHA is termed extravascular, whereas complement-mediated lysis of RBCs is termed intravascular AIHA. In order for intravascular AIHA to be recognizable, it requires overwhelming complement activation, therefore most AIHA is extravascular – be it IgG- or IgM-mediated.Diagnosis is made by first ruling out other causes of hemolytic anemia, such as G6PD, thalassemia, sickle-cell disease, etc. Clinical history is also important to elucidate any underlying illness or medications that may have led to the disease.Plentiful literature exists regarding the treatment of AIHA. Efficacy of treatment depends on the correct diagnosis of either warm- or cold-type AIHA.'Blood-induced icterus' produced by the release of massive amounts of a coloring material from blood cells followed by the formation of bile was recognized and described by Vanlair and Voltaire Masius' in 1871. About 20 years later, Hayem distinguished between congenital hemolytic anemia and an acquired type of infectious icterus associated with chronic splenomegaly. In 1904, Donath and Landsteiner suggested a serum factor was responsible for hemolysis in paroxysmal cold hemoglobinuria. French investigators led by Chauffard stressed the importance of red-cell autoagglutination in patients with acquired hemolytic anemia. In 1930, Lederer and Brill described cases of acute hemolysis with rapid onset of anemia and rapid recovery after transfusion therapy. These hemolytic episodes were thought to be due to infectious agents. A clear distinction between congenital and acquired hemolytic anemia was not drawn, however, until Dameshek and Schwartz in 1938, and, in 1940, they demonstrated the presence of abnormal hemolysins in the sera of patients with acquired hemolytic anemia and postulated an immune mechanism.In general, AIHA in children has a good prognosis and is self-limiting. However, if it presents within the first two years of life or in the teenage years, the disease often follows a more chronic course, requiring long-term immunosuppression, with serious developmental consequences. The aim of therapy may sometimes be to lower the use of steroids in the control of the disease. In this case, splenectomy may be considered, as well as other immunosuppressive drugs. Infection is a serious concern in patients on long-term immunosuppressant therapy, especially in very young children (less than two years).