Autoimmune hemolytic anemia
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| Autoimmune hemolytic anemia | |
| ICD-10 | D59.0-D59.1 |
|---|---|
| ICD-9 | 283.0 |
| MedlinePlus | 000579 |
| MeSH | D000744 |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Autoimmune hemolytic anemia (AIHA) is a type of hemolytic anemia where the body's immune system attacks its own red blood cells (RBCs), leading to their destruction (hemolysis). Antibodies and associated complement system components become fixed onto the RBC surface. These antibodies can be detected with the direct antiglobulin test, also known as the direct Coombs test. AIHA can also be induced by several drugs including methyl-dopa and fluarabine.
Autoimmunity must not be confused with alloimmunity.
Classification
Haemolysis can be intravascular or extravascular.
Intravascular haemolysis
Red blood cell lysis occurs in the circulation as a result of activation of the complement system cascade.
Extravascular haemolysis
Red Blood Cells that are coated with antibodies are specifically recognised in the reticuloendothelial system and destroyed by macrophages.
Subtypes
- Idiopathic
- Systemic lupus erythematosus
- Evans' syndrome (antiplatelet antibodies and haemolytic antibodies)
- Chronic lymphocytic leukemia
- Drugs (methyldopa)
- Cold antibody autoimmune hemolytic anemia
- Mixed-type autoimmune hemolytic anemia
Causes
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 being used synonymously). Idiopathic AIHA accounts for approximately 50% of cases.[1] Secondary AIHA can result from many other illnesses. Warm and cold type AIHA each have their own more common secondary causes. The most common causes of secondary warm-type AIHA include lymphoproliferative disorders (e.g. chronic lymphocytic leukemia, lymphoma) and other autoimmune disorders (e.g. systemic lupus erythematosis, rheumatoid arthritis, scleroderma, ulcerative colitis). Less common causes of warm-type AIHA include neoplasms other than lymphoid, and infection. Secondary cold type AIHA is also primarily caused by lymphoproliferative disorders, but is also commonly caused by infection, especially by mycoplasma, viral pneumonia, infectious mononucleosis and other respiratory infections. Less commonly, it can be caused by concomitant autoimmune disorders.[2]
Drug-induced AIHA, though rare, can be caused by a number of drugs, including α-methyldopa and penicillin. This is a type II immune response in which the drug binds to macromolecules on the surface of the RBCs and acts as an antigen. Antibodies are produced against the RBCs, which leads to complement activation. Complement fragments, such as C3a, C4a and C5a, activate granular leukocytes (e.g. neutrophils), while other components of the system (C6, C7, C8, C9) can either form the membrane attack complex (MAC) or can bind the antibody, aiding phagocytosis by macrophages (C3b). This is one type of "penicillin allergy".
Laboratory findings
- Positive direct Coombs test
- Anaemia
Treatment
Much literature exists regarding the treatment of AIHA. Efficacy of treatment depends on the correct diagnosis of either warm or cold type AIHA.
Warm type AIHA is usually a more insidious disease, not treatable by simply removing the underlying cause. First line therapy for this is usually with corticosteroids, such as prednisolone. Following this, other immunosuppressants are considered, such as rituximab, danazol, cyclophosphamide, azathioprine or cyclosporine.
Cold agglutinin disease is treated by avoiding the cold or sometimes with rituximab. Removal of the underlying cause is also important.
Paroxysmal cold hematuria is treated by removing the underlying cause, such as infection.
Related chapters
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- ↑ Gupta S, Szerszen A, Nakhl F; et al. (2011). "Severe refractory autoimmune hemolytic anemia with both warm and cold autoantibodies that responded completely to a single cycle of rituximab: a case report". J Med Case Reports. 5: 156. doi:10.1186/1752-1947-5-156. PMC 3096571. PMID 21504611.
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