Anaemia occurs when the blood doesn’t have enough red blood cells. This can happen if:
• The body doesn’t make enough red blood cells
• Bleeding causes the patient to lose red blood cells more quickly than they can be replaced
• The body destroys red blood cells
What red blood cells do …
The body makes three types of blood cells — white blood cells to fight infection, platelets to help the blood clot and red blood cells to carry oxygen throughout the body. Red blood cells contain haemoglobin — a red, iron-rich protein that gives blood its red color. Haemoglobin enables red blood cells to carry oxygen from the lungs to all parts of the body and to carry carbon dioxide from other parts of the body to the lungs so that it can be exhaled.
Most blood cells, including red blood cells, are produced regularly in the bone marrow — a red, spongy material found within the cavities of many of the large bones. To produce haemoglobin and red blood cells, the body needs iron, vitamin B-12, folate and other nutrients from the foods one eats.
Causes of common types of anaemia
Common types of anaemia and their causes include:
Iron deficiency anaemia. Iron deficiency anaemia is caused by a shortage of the element iron in the body. The bone marrow needs iron to make haemoglobin. Without adequate iron, the body cannot produce enough haemoglobin for red blood cells. This type of anaemia is often caused by blood loss, such as from heavy menstrual bleeding, an ulcer, cancer, a polyp somewhere in the digestive system, and prolonged use of aspirin or drugs known as nonsteroidal anti-inflammatory drugs (NSAIDs).
Vitamin deficiency anaemias. In addition to iron, the body needs folate and vitamin B-12 to produce sufficient numbers of healthy red blood cells. A diet lacking in these and other key nutrients can cause decreased red blood cell production. Additionally, some people may eat enough B-12, but their bodies aren’t able to process the vitamin. This can lead to vitamin deficiency anaemia.
Anaemia of chronic disease. Certain chronic diseases — such as cancer, HIV/AIDS, rheumatoid arthritis, Crohn’s disease and other chronic inflammatory diseases — can interfere with the production of red blood cells, resulting in chronic anaemia. Kidney failure also can cause anaemia.
Aplastic anaemia. This very rare life-threatening anaemia is caused by a decrease in the bone marrow’s ability to produce red blood cells. Causes of aplastic anaemia include infections, drugs and autoimmune diseases.
Anaemias associated with bone marrow disease. A variety of diseases, such as leukaemia and myelodysplasia, can cause anaemia by affecting blood production in the bone marrow. The effects of these types of cancer and cancer-like disorders vary from a mild alteration in blood production to a complete life-threatening shutdown of the blood-making process. Other cancers of the blood or bone marrow — such as multiple myeloma, myeloproliferative disorders and lymphoma — also can cause anaemia.
Haemolytic anaemias. This group of anaemias develops when red blood cells are destroyed faster than bone marrow can replace them. Certain blood diseases can cause increased red blood cell destruction. Haemolytic anaemias can be inherited, or patients can develop them later in life.
Sickle cell anaemia. This inherited and sometimes serious anaemia is caused by a defective form of haemoglobin that forces red blood cells to assume an abnormal crescent (sickle) shape. These irregular-shaped red blood cells die prematurely, resulting in a chronic shortage of red blood cells.
Other anaemias. There are several other rarer forms of anaemia, such as thalassaemia and anaemias caused by defective haemoglobin.