Anaemia

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.

Anaemia can also be defined physiologically by the degree of impairment of tissue oxygenation. Oxygen supply to tissues is controlled by a well-balanced mechanism that depends on the relative rate of oxygen supply and demand. Tissue oxygen delivery is dependent on the haemoglobin concentration, oxygen saturation and oxygen affinity, the degree and rate of change in blood volume, and the capacity for the cardiovascular and pulmonary systems to compensate.
These, in turn, determine the clinical manifestations of anaemia, on which the decision to transfuse should ultimately be based. Tissue oxygen delivery is also the major controlling factor of erythropoiesis through the synthesis and release of erythropoietin (EPO) by the proximal tubular cells or the peritubular interstitial cells in the kidney. EPO synthesis is governed by the activation of hypoxia inducible factor-1 (HIF-1), which controls the metabolic responses of multiple gene products to hypoxia. HIF-1 binds and activates the hypoxia-responsive transcriptional enhancer in the erythropoietin gene regulatory region that upregulates EPO expression. EPO stimulates erythroid precursor cells (CFU-E [colony-forming units—erythroid]), leading to increased proliferation and shortening of their maturation time. The marrow responds to increased EPO maximally in 4 to 7 days if enough iron is available.
Erythropoiesis can be increased by as much as a factor of 8. Typical of an endocrine loop feedback mechanism, there is an inverse relation between the hemoglobin and EPO levels measured in the blood. Although this relation holds true in simple iron deficiency, it is somewhat distorted in the anaemia associated with inflammation or chronic disease, in which there may be a blunted EPO response. This has made prediction of the haemoglobin response to treatment with exogenous EPO unpredictable, except in limited circumstances (see later).

These factors place a person at increased risk of anaemia:
• A diet lacking in certain vitamins. Choosing a diet that is consistently low in iron, vitamin B-12 and folate increases risk of anaemia.
• Intestinal disorders. Having an intestinal disorder that affects the absorption of nutrients in the small intestine — such as Crohn’s disease and celiac disease — puts a patient at risk for anaemia. Surgical removal of or surgery to the parts of the small intestine where nutrients are absorbed can lead to nutrient deficiencies and anaemia.
• Menstruation. In general, women who haven’t experienced menopause have a greater risk of iron deficiency anaemia than do men and postmenopausal women. That’s because menstruation causes the loss of red blood cells.
• Pregnancy. Pregnant women are at an increased risk of iron deficiency anaemia because their iron stores have to serve the increased blood volume as well as be a source of haemoglobin for the growing fetus.
• Chronic conditions. Patients who have cancer, kidney or liver failure or another chronic condition may be at risk for what’s called anaemia of chronic disease. These conditions can lead to a shortage of red blood cells. Slow, chronic blood loss from an ulcer or other source within the body can deplete the body’s store of iron, leading to iron deficiency anaemia.
• Family history. A family history of an inherited anaemia, such as sickle cell anaemia may also increase risk for the condition.
• Other factors. A history of certain infections, blood diseases and autoimmune disorders, alcoholism, exposure to toxic chemicals, and the use of some medications can affect red blood cell production and lead to anaemia.

Choose a vitamin-rich diet
Many types of anaemia can’t be prevented. However, iron deficiency anaemia and vitamin deficiency anaemias can be avoided by choosing a diet that includes a variety of vitamins and nutrients, including:
• Iron. Iron-rich foods include beef and other meats, beans, lentils, iron-fortified cereals, dark green leafy vegetables, and dried fruit.
• Folate. This nutrient, and its synthetic form folic acid, can be found in citrus fruits and juices, bananas, dark green leafy vegetables, legumes and fortified breads, cereals, and pasta.

• Vitamin B-12. This vitamin is found naturally in meat and dairy products. It’s also added to some cereals and soy products, such as soy milk.
• Vitamin C. Foods containing vitamin C — such as citrus fruits, melons and berries — help increase iron absorption.

Consider genetic counseling in patients with a family history of anaemia
Patients with a family history of an inherited anaemia, such as sickle cell anaemia or thalassemia should talk to their doctor and possibly a genetic counsellor about their risk and what risks they may pass on to their children.

Anaemia treatment depends on the cause.
• Iron deficiency anaemia. This form of anaemia is treated with changes in the diet and iron supplements. If the underlying cause of iron deficiency is loss of blood — other than from menstruation — the source of the bleeding must be located and stopped. This may involve surgery.
• Vitamin deficiency anaemias. Folic acid and vitamin C deficiency anaemias are treated with dietary supplements and increasing these nutrients in the diet. If the patient’s digestive system has trouble absorbing vitamin B-12 from the food they eat, they may receive vitamin B-12 injections.
• Anaemia of chronic disease. There’s no specific treatment for this type of anaemia. Doctors focus on treating the underlying disease. If symptoms become severe, a blood transfusion or injections of synthetic erythropoietin, a hormone normally produced by the kidneys, may help stimulate red blood cell production and ease fatigue.
• Aplastic anaemia. Treatment for this anaemia may include blood transfusions to boost levels of red blood cells. Patients may need a bone marrow transplant if their bone marrow is diseased and cannot make healthy blood cells.
• Anaemias associated with bone marrow disease. Treatment of these various diseases can range from simple medication to chemotherapy to bone marrow transplantation.
• Haemolytic anaemias. Managing haemolytic anaemias includes avoiding suspect medications, treating related infections and taking drugs that suppress the patient’s immune system, which may be attacking their red blood cells. Short courses of treatment with steroids or immune suppressant medications can help suppress the immune system’s attack on the red blood cells. Depending on the severity of the anaemia, a blood transfusion or plasmapheresis may be necessary. Plasmapheresis is a type of blood-filtering procedure. In certain cases, removal of the spleen can be helpful.
• Sickle cell anaemia. Treatment for this anaemia may include the administration of oxygen, pain-relieving drugs, and oral and intravenous fluids to reduce pain and prevent complications. Doctors may also recommend blood transfusions, folic acid supplements and antibiotics. A bone marrow transplant may be an effective treatment in some circumstances. A cancer drug called hydroxyurea also is used to treat sickle cell anaemia.
• Thalassemia. This anaemia may be treated with blood transfusions, folic acid supplements, removal of the spleen (splenectomy), a bone marrow transplant or a cancer drug.

To diagnose anaemia, the doctor may recommend:
• Physical examination. During a physical exam, the doctor may listen to the patient’s heart and their breathing. The doctor may also place his or her hands on the patient’s abdomen to feel the size of their liver and spleen.
• Complete blood count (CBC). A CBC is used to count the number of blood cells in a sample of the patient’s blood. For anaemia, the doctor will be interested in the levels of the red blood cells contained in the blood (haematocrit) and the haemoglobin in the blood. Normal adult haematocrit values vary from one medical practice to another but are generally between 38.8 and 50 percent for men and 34.9 and 44.5 percent for women. Normal adult haemoglobin values are generally 13.5 to 17.5 grams per deciliter for men and 12 to 15.5 grams per deciliter for women.
• A test to determine the size and shape of red blood cells. Some red blood cells may also be examined for unusual size, shape and colour. Doing so can help pinpoint a diagnosis. For example, in iron deficiency anaemia, red blood cells are smaller and paler in color than normal. In vitamin deficiency anaemias, red blood cells are enlarged and fewer in number.

Additional tests
In patients who receive a diagnosis of anaemia, their doctor may order additional tests to determine the underlying cause. For example, iron deficiency anaemia can result from chronic bleeding of ulcers, benign polyps in the colon, colon cancer, tumors or kidney failure. The doctor may test for these and other conditions that may be causing the anaemia.
Occasionally, it may be necessary to study a sample of the patient’s bone marrow to diagnose anaemia.