Aplastic anaemia

Cytotoxic drugs are those that are designed to be directly toxic to cells in the treatment of cancer. Some destroy bone marrow cells (for example, in the treatment of leukaemia). Normally the marrow recovers after a short period. An overdose of these drugs causes severe, prolonged aplasia.

Radiotherapy (treatment with X-rays) suppresses the bone marrow, and may be intentionally used to do so in preparation for bone marrow transplantation. The use of these treatments should be confined to specialised centres where careful monitoring of the blood count takes place.

Some cases of aplastic anaemia have occurred after viral infections. In particular, hepatitis A, hepatitis B and 'non-A, non-B, non-C' hepatitis have been implicated, and more rarely the Epstein-Barr virus.

Very rarely aplastic anaemia occurs during pregnancy. It is not clear whether this is just a coincidence. Sometimes the disease recovers spontaneously at the end of pregnancy.

What is the disease process?

. Nowadays, treatment of aplastic anaemia is directed on the assumption that the disease is related to the immune system.

The first evidence for this came from the early days of bone marrow transplantation. Sometimes the marrow that regrew after the conditioning treatment was of the person's own type rather than that of the donor. This implied that there had been an immune attack going on in the person's bone marrow, which was relieved by the intense dampening down of his or her immune system by the treatment.

Other evidence comes from immunodeficient individuals (ie those with impaired immunity either through disease or caused by their treatment) who receive a blood transfusion. They sometimes develop transfusion-related graft-versus-host disease (GvHD) – in other words a rejection response. One of the forms that it can take is aplastic anaemia, demonstrating that an immunological attack can cause aplastic anaemia.

What are the symptoms?

The person complains of increasing tiredness, weakness and shortness of breath. Bleeding, bruising and blood spots may be noticed.

Sore throats and other infections are noticeable. A high temperature with shivering attacks is an important symptom that demands immediate medical attention.

How is aplastic anaemia diagnosed?

The following combination of three symptoms should raise suspicion of bone marrow failure:

- anaemia - tiredness, weakness and breathlessness
- low white cell count in the blood (neutropenia) - fever, sore throat, shivering attacks
- low platelet count (thrombocytopenia) - bruising and bleeding.

On examination the doctor may find pale skin, possibly the signs of heart failure, bruises and petechiae (small blood spots in the skin and mouth), mouth ulcers and fever.

An important negative finding is the absence of enlarged lymph nodes or an enlarged spleen. Their presence would point to other diagnoses, such as lymphoma or leukaemia.

The most important test is the full blood count, which will show reduced numbers of red cells, white cells (neutropenia) and platelets (thrombocytopenia) - in other words all of the cellular components of blood. This feature is called pancytopenia.

The level of the neutrophil count defines the severity of the disease. Neutrophils are normally the most numerous of the various types of white cell we have in our blood and they are particularly involved in combating infection by bacteria and fungi.

- Counts below 0.5 x 109/L mean severe aplastic anaemia.
- Counts below 0.2 x 109/L mean very severe aplastic anaemia.

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