Anemia

  • Basics

    Anemia occurs when red blood cells are reduced in number. Red blood cells are a major component of blood and serve the vital function of delivering oxygen from the lungs to the rest of the tissues in the body. When anemia occurs, the body is deprived of the oxygen it needs to function properly.

    There are many types of anemia, all of which have their own treatments. The most common types include:

    • iron-deficiency anemia
    • folic acid-deficiency anemia
    • anemia from vitamin B12 deficiency.

    Anemia may be a consequence of a chronic disease, medication, or excessive alcohol consumption. In some cases, inherited conditions that produce blood defects result in anemia.

    Most cases of anemia are corrected simply by adding more iron or folic acid to the diet. If you have a deficiency of vitamin B12, you may require intramuscular injections. Some cases are not as easily remedied.

    A person who is slightly anemic may feel tired and weak and look pale. Getting winded and having chest pains during exercise are other symptoms of anemia. In more serious cases, heartbeat irregularities or neurological symptoms such as confusion, irritability, and numbness or tingling in the extremities appear.

  • Causes

    Iron-deficiency anemia is the most common type of the disease, and is most often caused by excessive blood loss. When the body loses blood, it loses iron—a key part of red blood cells. Iron is needed to make hemoglobin, the protein in red blood cells that carries oxygen. Gradual, prolonged blood loss from heavy menstruation is the primary cause of iron-deficiency anemia in women. Gastrointestinal bleeding from hemorrhoids, a stomach ulcer, or an inflammatory bowel condition may also make a person anemic. Blood loss due to colon cancer and other intestinal cancers accounts for about 2% of cases. Long-term use of aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen can irritate the stomach lining and cause bleeding that produces anemia. Women who are pregnant or breast-feeding sometimes become anemic when their increased iron needs are not met. Growing children, who also need more iron, occasionally become anemic. However, dietary lack is rarely the cause of iron-deficiency anemia.

    Folic acid deficiency is a type of anemia that develops when there is too little folic acid consumed in the diet, or when it is not properly absorbed in the body. The body needs folic acid to make red blood cells. Too little of this vitamin (also called folate) results in red blood cells that are abnormally large (macrocytic), and die prematurely. The body does not store folic acid in large amounts, and therefore folic acid levels need to be sustained through diet. Folic acid-deficiency anemia is caused by an inadequate intake or inability to absorb the vitamin. At certain times, such as during pregnancy and breast-feeding, the body needs more folic acid than usual. Most pregnant women are advised to take a supplement (which prevents birth defects), and the government now requires that many foods (cereals, breads, pastas) be fortified with the vitamin. People with gastrointestinal illnesses and cancers may have problems absorbing folic acid, and become anemic. Likewise, people taking certain drugs (anticonvulsants, antibiotics, birth control, pills, anticancer agents) sometimes have difficulty absorbing or metabolizing folic acid.

    Pernicious anemia is a less common but serious condition that develops when the body cannot absorb vitamin B12. Pernicious anemia is a disorder in which the immune system attacks cells in the stomach that produce intrinsic factor (IF)—a substance needed to transport vitamin B12. Without IF, a B12 deficiency develops and red blood cells grow too large and die too early. Pernicious anemia sometimes arises after intestinal surgery or from an intestinal problem than impairs metabolism of this vitamin. In older people, deterioration of the stomach lining (atrophic gastritis) and subsequent failure to produce IF is a common cause. Diet is rarely implicated in B12 deficiency, though it can be the culprit in strict vegetarians, or vegans, who do not eat any meat or dairy products, which are rich in the vitamin.

    Chronic diseases such as cancer, rheumatoid arthritis, HIV/AIDS, or alcoholism, and certain medications can also cause anemia. Chronic kidney disease is also an important cause of chronic anemia. People with cancers that affect the bone marrow, which is where the majority of red blood cells are produced, often become anemic; so do people with diseases that trigger the inflammatory process, such as rheumatoid arthritis, lupus, Grave's disease, Crohn's disease, and ulcerative colitis. Cytokines, which are proteins released during inflammation, seem to be responsible. Cytokines are essential for healing, but in excess they can interfere with iron and the hormone responsible for stimulating the production of red blood cells (erythropoietin).

    Alcoholics sometimes develop anemia because of a nutritional deficiency. Alcohol hampers vitamin absorption, and alcoholics tend to eat poorly.

    Medications can also cause anemia. Long-term use of NSAIDs may induce bleeding that results in anemia. Drugs that suppress the immune system and fight cancer can lead to aplastic anemia—anemia that occurs when the bone marrow doesn't make enough red blood cells. Additionally, certain antibiotics, blood pressure medications, and drugs used to treat heart arrythmias rarely can cause hemolytic anemia—anemia that occurs when red blood cells are destroyed prematurely.

    Rare but serious anemias such as sickle cell anemia and thalassemia are inherited. As the name implies, sickle cell anemia is characterized by sickle-shaped red blood cells. These cells are stiff, and cannot pass through the blood vessels very well. Consequently, they die after about 20 days (the average life span for a normal red blood cell is 120 days). The resulting anemia, which affects about 0.6% of the population, is serious, and can be deadly. Thalassemia is an inherited blood disorder that stems from a defect in the rate at which hemoglobin is produced. The two main types are thalassemia major (Cooley's anemia) and thalassemia minor (the more common of the two). Thalassemia can be very serious, but the condition is rare; it is more commonly found in people of Mediterranean descent.

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