Aplastic anemia
| Aplastic anemia | |
|---|---|
| Specialty | Hematology  |
Aplastic anaemia is a condition where the bone marrow does not produce enough, or any, new cells to replenish the blood cells.
The term 'aplastic' refers to the inability of the marrow to function properly. Anaemia is the condition of having fewer blood cells than normal, or fewer than needed to function properly. Typically, anaemia refers to low red blood cell counts, but aplastic anaemia patients have lower counts on all three blood cell types: red blood cells, white blood cells, and platelets.
Causes
One known cause is an autoimmune disorder, where the white blood cells attack the bone marrow.
In many cases, the etiology is impossible to determine, but aplastic anaemia is sometimes associated with exposure to substances such as benzene, radiation, or to the use of certain drugs, including chloramphenicol and phenylbutazone.
Signs and symptoms
- Anaemia with malaise, pallor and associated symptoms
- Thrombocytopenia (low platelet counts), leading to increased risk of haemorrhage and bruising
- Leukopenia (low white blood cell count), leading to increased risk of infection
Diagnosis
The diagnosis can only be made on bone marrow biopsy. Before this procedure is undertaken, a patient will generally have had other blood tests to find diagnostic clues, including a full blood count, renal function and electrolytes, liver enzymes, thyroid function tests, vitamin B12 and folic acid levels.
Treatment
Treating aplastic anaemia involves suppression of the immune system, an effect achieved by daily medicine intake, or, in more severe cases, a bone marrow transplant, a potential cure but a risky procedure. The transplanted bone marrow replaces the failing bone marrow cells with new ones from a matching donor. The pluripotent stem cells in the bone marrow reconstitute all three blood cell lines, giving the patient a new immune system, red blood cells, and platelets. However, besides the risk of graft failure, there is also a risk that the newly created white blood cells may attack the rest of the body ("graft-versus-host disease").
Medical therapy of aplastic anaemia often includes a short course of anti-thymocyte globulin (ATG or anti-lymphocyte globulin) and several months of treatment with cyclosporin to modulate the immune system. Mild chemotherapy with agents such as cyclophosphamide and vincristine may also be effective. Antibodies therapy, such as ATG, targets T-cells, which are believed to attack the bone marrow. Steroids are generally ineffective.
In the past, before the above treatments became available, patients with low leukocyte counts were often confined to a sterile room or bubble (to reduce risk of infections), as in the famed case of Ted DeVita.
Follow-up
Regular full blood counts are required to determine whether the patient is still in a state of remission.
10-33% of all patients develop the rare disease paroxysmal nocturnal haemoglobinuria (PNH, anaemia with thrombopenia and/or thrombosis), which has been explained as an escape mechanism by the bone marrow against destruction by the immune system. Flow cytometry testing is probably warranted in all PNH patients with recurrent aplasia.
See also
External links
- Aplastic Anemia & MDS International Foundation
- Mayo Clinic
- University of Texas
- MedlinePlus Encyclopedia: 000554 -- Idiopathic aplastic anemia
- MedlinePlus Encyclopedia: 000529 -- Secondary aplastic anemia