What is aplastic anaemia?

The bone marrow is the soft fatty tissue found in the cavities of our bones. Basically it is the "factory" where most of our blood cells - red cells, platelets and white cells - are made. Aplastic anaemia (or bone marrow failure) is a serious rare disease that develops when the bone marrow fails to produce these blood cells.

What are the symptoms of aplastic anaemia?

Patients may have symptoms of anaemia such as paleness, fatigue, shortness of breath on exertion and rapid heart rate (caused by low red cells); excessive bleeding and a tendency to bruise easily (low platelets) and a high susceptibility to infection (lack of white cells).

How is it diagnosed?

A diagnosis of aplastic anaemia cannot be made on the results of a blood test alone as there are other diseases that can also cause low blood counts. A sample of bone marrow is taken from inside the bone - usually the hip bone - using a needle (bone marrow aspirate) along with a sample of the bone itself (bone marrow trephine). These samples are analysed and a diagnosis made.

How is aplastic anaemia classified?

Aplastic anaemia can be divided into three groups - non-severe aplastic anaemia (NSAA), severe aplastic anaemia (SAA) and very severe aplastic anaemia (VSAA).

In non-severe aplastic anaemia the blood counts are low but the condition is not severe enough to be classified as severe. Patients may be in need of transfusions of red blood cells but not usually platelets. They are not usually at risk from infection.

In severe aplastic anaemia, two of the following are present:

• a low platelet count ie less than 20 (normal range is between 150 to 400);
• a reticulocyte count of less than 25 (normal range is between 50 and 150);
• an absolute neutrophil count of less than 0.5 (normal range is between 1.5 to 8.0);

Very severe aplastic anaemia is the same as severe aplastic anaemia but the absolute neutrophil count is very low at less than 0.2.

What causes aplastic anaemia?

It is thought that in the majority of cases, the damage to the bone marrow stem cells is caused by an auto-immune reaction. This happens when the immune system becomes "confused" and starts to attack the body's own tissues. As this reaction has no clear underlying cause it is known as idiopathic aplastic anaemia.

In other cases, there are certain factors that can trigger an auto-immune reaction. These factors include certain drugs, some chemicals and certain diseases and infections.

What are the treatment options for aplastic anaemia?

Treatment of aplastic anaemia is classed as either "supportive therapy" or "definitive therapy". Supportive therapy means treating the symptoms of low blood counts with transfusions and antibiotics. Definitive therapy aims to restore a healthy, working bone marrow so that the patient doesn't need transfusions and can live a normal life.

The only real "cure" for aplastic anaemia is a bone marrow transplant. Transplants are usually carried out in patients under the age of 40 who have a brother or sister as a suitable match. In some cases where a sibling donor isn't available, a matched unrelated donor (MUD) transplant can be carried out using a donor from a volunteer donor registry. However the risks are higher with a MUD transplant than with a sibling one.

For patients where a transplant is not an option, immunosuppressive therapy called antilymphocyte globulin (ALG) is used. This treatment suppresses or "damps down" the immune system allowing the bone marrow to recover. 

The British Society for Haematology has produced Guidelines for the diagnosis and management of acquired aplastic anaemia. The purpose of these guidelines is to provide a rational approach to the investigation and management of patients with acquired aplastic anaemia. You can read the guidelines by clicking on the link to the BSH website