Disorders in which haemoglobin (the oxygen-carrying pigment in red blood cells) is deficient or abnormal
- Age, gender, genetics, and lifestyle as risk factors depend on the type
Anaemia is a deficiency or an abnormality of haemoglobin, the component of red blood cells that binds with oxygen from the lungs and carries it through the circulation to the body tissues. The oxygen-carrying capacity of the blood is thus reduced, and the tissues of the body may not receive sufficient oxygen.
Red blood cells are manufactured in the bone marrow (at the rate of more than a million every second) and circulate in the bloodstream for about 120 days before they are broken down in the spleen. In a healthy person, the production and destruction of red blood cells are balanced. Anaemia occurs if this balance is upset, reducing the number of healthy cells, or if the haemoglobin is abnormal.
What are the types?
There are four main types of anaemia. The first type is due to a deficiency of one or more of the substances that are essential for the formation of healthy red blood cells. By far the most common form is iron-deficiency anaemia, which results from low levels of iron in the body. A much rarer form is megaloblastic anaemia, which is usually the result of low levels of either vitamin B12 or another vitamin, folic acid, in the body.
The second type of anaemia results from inherited abnormalities of haemoglobin production. Examples of this type include sickle-cell disease and thalassaemia. The haemoglobin is abnormal from shortly after birth, but symptoms of anaemia may not develop until later in childhood.
The third type of anaemia is caused by excessively rapid destruction of red blood cells (haemolysis) and is called haemolytic anaemia.
The fourth type of anaemia, called aplastic anaemia, is caused by failure of the bone marrow to produce sufficient numbers of red blood cells and often of other types of blood cell as well.
Anaemia may be due to a combination of different causes, and sometimes the exact cause of the condition is not known. In some cases, anaemia develops during a long-term illness, such as cancer or rheumatoid arthritis.
What are the symptoms?
If your anaemia is mild, your body may be able to make up for a slight reduction in the oxygen-carrying capacity of blood by increasing the blood supply to the tissues. In this case, there may not be any symptoms. Symptoms of more severe anaemia may include:
Tiredness and a feeling of faintness.
Shortness of breath on mild exertion.
You may also have a rapid heart rate because the heart has to work harder to increase blood supply to the rest of the body. Stress on the heart may result in chronic heart failure, common symptoms of which are swollen ankles and increasing shortness of breath.
What might be done?
Anaemia is usually confirmed by blood tests to measure the level of haemoglobin and to establish the type and cause of the anaemia. A bone marrow aspiration and biopsy may be carried out to obtain tissue samples for examination under a microscope.
Most anaemias respond well to treatment. Severe cases may require blood transfusion.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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