Article: Aplastic anemia

Aplastic anemia 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. Anemia is the condition of having fewer blood cells than normal, or fewer than needed to function properly. Typically, anemia refers to low red blood cell counts, but aplastic anemia 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 anemia 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

• Anemia with malaise, pallor and associated symptoms
• Thrombocytopenia (low platelet counts), leading to increased risk of hemorrhage 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 anemia involves suppression of the immune system, an effect achieved by daily medicine intake, or, in more severe cases, a bone marrow transplant, a curing but risky procedure. Bone marrow transplant replaces the old bone marrow cells with new ones from a donor, giving the patient a new immune system. There is a risk that the newly created white blood cells may attack the rest of the body ("graft-versus-host disease").

Medical therapy of aplastic anemia often includes a short course of anti-thymocyte globulin (ATG or anti-lymphocyte globulin) and several months of treatment with ciclosporin 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.

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 hemoglobinuria (PNH, anemia 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

• Fanconi anemia
• Acquired pure red cell aplasia