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Autoimmune Hemolytic Anemia
Autoimmune hemolytic anemia is a group of disorders characterized by a malfunction of the immune system that produces autoantibodies, which attack red blood cells as if they were substances foreign to the body.
Autoimmune hemolytic anemia is an uncommon group of disorders that can occur at any age. These disorders affect women more often than men. About half of the time, the cause of autoimmune hemolytic anemia cannot be determined (idiopathic autoimmune hemolytic anemia). Autoimmune hemolytic anemia can also be caused by or occur with another disease, such as systemic lupus erythematosus, and it can follows the use of certain drugs, such as penicillin.
Destruction of red blood cells by autoantibodies may occur suddenly, or it may develop gradually. In some people, the destruction may stop after a period of time; whereas in other people, it persists and becomes chronic. There are two main types of autoimmune hemolytic anemia: warm antibody hemolytic anemia and cold antibody hemolytic anemia. In the warm antibody type, the autoantibodies attach to and destroy red blood cells at temperatures equal to or in excess of normal body temperature. In the cold antibody type, the autoantibodies become most active and attack red blood cells only at temperatures well below normal body temperature.
Some people with autoimmune hemolytic anemia may have no symptoms, especially when the destruction of red blood cells is mild and develops gradually. Others have symptoms similar to those that occur with other types of anemia, especially when the destruction is more severe or rapid. When severe or rapid destruction of red blood cells occurs, mild jaundice may also develop. When destruction persists for a few months or longer, the spleen may enlarge, resulting in a sense of abdominal fullness and, occasionally, discomfort.
When the cause of autoimmune hemolytic anemia is another disease, symptoms of the underlying disease, such as swollen and tender lymph nodes and fever, may dominate.
Once a doctor diagnoses anemia, increased destruction of red blood cells is suspected when a blood test shows an increase in the number of red blood cells that are immature (reticulocytes). Alternatively, a blood test may show an increased amount of a substance called bilirubin and a decreased amount of a protein called haptoglobin.
Autoimmune hemolytic anemia as the cause is confirmed when blood tests detect increased amounts of certain antibodies, either attached to red blood cells (direct antiglobulin or Coombs test) or in the liquid portion of the blood (indirect antiglobulin or Coombs test). Other tests sometimes help determine the cause of the autoimmune reaction that is destroying red blood cells.
If symptoms are mild or if destruction of red blood cells seems to be slowing on its own, no treatment is needed.
If a drug has caused the problem, the offending drug needs to be stopped.
If red blood cell destruction is worsening, a corticosteroid drug such as prednisone is usually the first choice for treatment. High doses are used at first, followed by a gradual tapering of the dose over many weeks or months.
I.V.I.g may be used when steroids are ineffective.
When people do not respond to corticosteroids or when the corticosteroid causes intolerable side effects, surgery to remove the spleen (splenectomy) is often the next treatment. When destruction of red blood cells persists after removal of the spleen or when surgery cannot be performed, immunosuppressive drugs, such as cyclophosphamide or azathioprine, are used.
Plasmapheresis, which involves filtering blood to remove antibodies, is occasionally helpful when other treatments fail. When red blood cell destruction is severe, blood transfusions are sometimes needed, but they do not treat the cause of the anemia and provide only temporary relief.
Role of intravenous immunoglobulin G in autoimmune hematologic disorders.
The data presented in this review established IVIG therapy as an important treatment modality in the autoantibody-mediated cytopenias and coagulation disorders of both children and adults. The immediate response to therapy is thought to be related to nonspecific Fc-receptor blockade of mononuclear phagocytes in the reticuloendothelial system (autoimmune cytopenias), or to idiotypic antibody interaction with pathologic autoantibodies (in acquired coagulation disorders). Although less frequent, long-term responses to IVIG therapy are reported. Such responses must involve an immunomodulating effect of IgG that influences T- and B-cell function, with inhibition of pathologic autoantibody formation. It is possible that idiotypic antibody interactions play a part in long-term responses. The experience with IVIG therapy in the decade following Imbach's important observations reported in 1981 has provided a sound data base regarding the use of this important therapy in patients with autoimmune hematologic disorders. The challenge of the next decade should be to further investigate mechanisms of action of this important therapy and to conduct carefully controlled studies to answer specific clinical questions. Examples of such questions include the following: (1) Can IVIG therapy, administered early in the course of illness in selected children with acute ITP, decrease the incidence of chronic ITP?; (2) Is maintenance, high-dose IVIG therapy a cost-effective method for the management of patients with chronic ITP refractory to corticosteroid therapy and splenectomy?; and (3) Can IVIG therapy administered to selected pregnant women with ITP significantly reduce the incidence of serious thrombocytopenia in their offspring? In conducting these studies, consideration should be given to the type of IVIG preparation used and to the treatment protocol implemented. It is evident that responses to unmodified IgG preparations (with the Fc-receptor part of the molecule left largely intact) are superior to preparations that have been modified during preparation. Responses are also likely to be dose-related. The data reported for IVIG therapy in patients with acquired factor VIII deficiency suggests that the idiotypic antibody content of IgG preparations is also of importance; if so, preparations selected from specific donor pools (for example, multiparous women) known to contain higher levels of circulating autoantibodies (than those from primiparous women or untransfused males) may provide a degree of benefit not seen with standard IVIG preparations. It is therefore important that clinicians and laboratory specialists work closely together in the design and conduct of future clinical trials initiated to answer those important clinical questions raised by the first decade of observations with IVIG therapy for autoimmune hematologic disorders.