A type of anaemia caused by excessive destruction of red blood cells
- Genetics as a risk factor depends on the cause
- Age, gender, and lifestyle are not significant factors
Haemolytic anaemia occurs when the red cells in the blood are broken down more rapidly than they can be replaced. Red blood cells usually have a lifespan of about 120 days before they are destroyed in the spleen, a process known as haemolysis. The premature destruction of red blood cells may be caused by abnormal immune reactions, inherited disorders, or infections. If the bone marrow cannot replace the red blood cells rapidly, haemolytic anaemia results.
What are the causes?
Haemolytic anaemia is commonly due to an abnormal immune reaction in which the body produces antibodies that attack red blood cells and encourage their destruction in the spleen. This reaction is often triggered by drugs, including penicillin (see Antibiotics), methyldopa (see Antihypertensive drugs), or quinine (see Antimalarial drugs). Antibodies that attack red blood cells may also occur in people who have chronic lymphocytic leukaemia or an autoimmune disorder such as systemic lupus erythematosus.
Inherited disorders that affect the red blood cells’ biochemical make-up or shape may also promote haemolysis. One such biochemical abnormality, affecting more than 100 million people worldwide, is lack of G6PD (glucose-6-phosphate dehydrogenase), an enzyme in red blood cells that helps to protect them against chemical damage. People with the disorder are usually well but infection and certain drugs can trigger haemolysis. In one form of G6PD deficiency, which mostly affects people of Mediterranean origin, severe haemolysis is triggered by a chemical found in broad beans (favism).
Other inherited disorders that can lead to haemolytic anaemia include thalassaemia, sickle-cell disease, and hereditary spherocytosis. In thalassaemia, large numbers of abnormal red blood cells are destroyed by the spleen. In sickle-cell disease, the sickle-shaped red blood cells are abnormally fragile and may be destroyed prematurely. In spherocytosis, the red blood cells change to a spherical shape and are destroyed prematurely in the spleen. All of these disorders may lead to continuous haemolysis from childhood.
Red blood cells may also be destroyed as a result of infections such as malaria in which the infective organism multiplies within the red blood cells. Rarely, haemolytic anaemia is due to damage to the red blood cells caused by an artificial heart valve.
What are the symptoms?
If you have haemolytic anaemia, you may notice the following symptoms, which are common to all anaemias:
Tiredness and a feeling of faintness.
Shortness of breath on mild exertion.
You may also have symptoms that occur as a result of haemolysis, including:
Yellowing of the skin and whites of the eyes (see Jaundice).
Swelling of the abdomen caused by enlargement of the spleen as it filters out many damaged red blood cells.
Over a period of several years, you may develop gallstones, which form from bilirubin, a product of the breakdown of red blood cells.
What might be done?
Haemolytic anaemia can be diagnosed from blood tests that reveal numerous immature red blood cells and, in some cases, fragmented, abnormally shaped red blood cells. Your doctor may also measure your blood levels of bilirubin, and he or she may arrange for blood tests to look for antibodies to red cells to identify the cause of the anaemia.
Underlying disorders, such as an infection or autoimmune disease, will be treated and any drugs that are causing haemolysis will be stopped. Corticosteroids may be given for haemolytic anaemia due to an immune reaction. In some cases of haemolytic anaemia, surgical removal of the spleen is necessary.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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