Aplastic anemia is a condition where the bone marrow does not produce enough, or any, new cells to replenish the blood cells. 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 or to the use of certain drugs, including chloramphenicol and phenylbutazone.

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.

Signs and symptoms

• Anemia with malaise, pallor and associated symptoms
• Thrombocytopenia (low platelet counts), leading to increased risk of hemorrhage and bruising
• Neutropenia

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. An interesting property of bone marrow transplants is the production of new white blood cells, an effect that removes the possibility of rejection. However, newly created white blood cells might reject the whole body instead ("graft-versus-host disease").

Steroids are generally ineffective, and many patients eventually receive mild chemotherapy to silence the immune system. This usually happens with the agents cyclophosphamide and vincristine.

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 will recurrent aplasia.