Anaemia is a disease that occurs when the number of red blood cells (RBCs) and/or the amount of haemoglobin found in the red blood cells falls below normal. Red blood cells and the haemoglobin contained within them are necessary for moving oxygen from the lungs to the rest of the body. Without an adequate supply of oxygen, many parts of the body will not work properly. Anaemia can be mild, moderate or severe depending on how much the RBC count and/or haemoglobin levels have fallen. It is a fairly common condition and affects both men and women of all ages and ethnic groups. Certain people are at an increased risk of developing anaemia. These include people with diets poor in iron and some vitamins, long lasting illnesses such as kidney disease, diabetes, cancer, inflammatory bowel disease, a family history of inherited anaemia, longstanding infections such as tuberculosis or HIV and those who have had significant blood loss from injury or surgery.
In general, anaemia has two main causes:
- Impaired or decreased production of RBCs as can occur in iron deficiency, B vitamin deficiencies or a number of diseases affecting the bone marrow’s ability to make red blood cells.
- Decreased survival or increased destruction of red blood cells as can occur in bleeding or haemolysis. There are several different types of anaemia and various causes. Some of the most common types are given in the table below. Click on the links to read more about each one. Some patients may have more than one cause of anaemia.
|Type of Anaemia||Description||Examples of Causes|
|Iron Deficiency||Lack of iron leads to decreased amounts haemoglobin; low levels of haemoglobin in turn leads to decreased production of normal RBCs||Blood loss; diet low in iron; poor absorption of iron|
|Pernicious Anaemia and B Vitamin Deficiency||Lack of B vitamins (particularly B12) does not allow RBCs to grow and then divide as they normally would during development; leads to decreased production of normal RBCs||Lack of intrinsic factor; diet low in B vitamins; decreased absorption of B vitamins with illnesses such as Crohn's disease or after surgical removal of parts of the bowel|
|Aplastic||Decreased production of all cells produced by the bone marrow of which RBCs are one type. "Pure red cell aplasia" is similar disease where only production of the red blood cells is affected.||Idiopathic Aplastic Anaemia, Cancer therapy, exposure to toxic substances, autoimmune disorders, viral infections, inherited disorders|
|Haemolytic||RBCs survive less than the normal 120 days in the circulation; leads to a decrease in the numbers of RBCs||Inherited causes include sickle cell and thalassemia; other causes include transfusion reaction, autoimmune disease, certain drugs|
|Anaemia of Chronic Diseases||Various illnesses over a long time can reduce the production of RBCs||Autoimmune disease such as rheumatoid arthritis, kidney disease, diabetes, longstanding infections including tuberculosis or HIV|
Anaemia may be acute or chronic – which means fast-developing or longstanding. Chronic anaemia may develop slowly over a period of time with long-term illnesses such as rheumatoid arthritis, diabetes, chronic kidney disease or cancer. In these situations the anaemia may not be apparent because symptoms are hidden by the main disease. The presence of anaemia in chronic conditions may be missed for a period of time and only discovered from tests or examinations for other conditions.
Anaemia may also occur in acute episodes such as with bleeding or with certain haemolytic anaemias in which the red blood cells are destroyed. Signs and symptoms may develop quickly and the cause found from a physical examination, medical history and testing.
Signs and Symptoms
Though different types of anaemia have different causes, the signs and symptoms can be very similar. Mild or moderate forms of anaemia may cause few if any symptoms. The most common symptoms are:
- a general feeling of tiredness, lack of energy or weakness (fatigue)
- pale complexion
Other signs and symptoms that may develop as the anaemia becomes more severe include headache, dizziness, feeling of cold or numbness in hands and/or feet, pale complexion, fast or irregular heartbeat and chest pain. Some patients complain of hearing a pounding sound (their pulse) in their ears.
Full Blood Count (FBC)
Anaemia may first be detected when a full blood count (FBC) is done as part of a health check or during investigations for another illness. FBC is a routine test that counts the number and relative proportion of each of the different types of cells in your blood. It gives your doctor information about the size, shape, and relative maturity of the blood cells present in your blood at that moment.
Blood Film and Differential
If results of the FBC indicate anaemia, it may be followed up with an examination of a blood film or a differential. Results from these tests may give clues to the cause of the anaemia. Several other tests can help discover the cause of the anaemia and then guide treatment. See the individual discussions of the different types of anaemia for more on these.