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| :''This article discusses anemia, the medical condition. For the fern genus, see ]. | :''This article discusses anemia, the medical condition. For the fern genus, see ]. | ||
| '''Anemia''' (]) or '''anaemia''' (]) is |
'''Anemia''' (]) or '''anaemia''' (]) is a reduced ability of ] to transfer ] to the ] due to a shortage in ]s or abnormalities in their function. ] (the oxygen-carrying ] in the red blood cells) has to be present to ensure adequate oxygenation of all body tissues. | ||
| There are several kinds of anemia, produced by a variety of underlying causes. |
Anemia is the most common disorder of the blood. There are several kinds of anemia, produced by a variety of underlying causes. Anemia is classified by the size of the red blood cell: decreased (''microcytic''), normal (''normocytic'') or enlarged (''macrocytic'' or ''megaloblastic''). | ||
| ==Signs and symptoms== | |||
| ==Classification based on size of the red blood cells== | |||
| Anemia goes undetected in many people, and symptoms can be vague. Most commonly, a feeling of weakness or fatigue is reported. ] is reported in more severe cases. Very severe anemia prompts a compensatory response where ] is markedly increased, leading to ]s and sweatiness; this process can lead to ] in elderly people. | |||
| ⚫ | |||
| Pallor (pale skin and mucosal linings) is only notable in cases of severe anemia, and is therefore not a reliable sign. | |||
| ⚫ | ===Macrocytic anaemia=== | ||
| ⚫ | The |
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| ==Diagnosis== | |||
| ⚫ | ===Normocytic anaemia=== | ||
| The only way to diagnose anemia is with a ]. Generally, a ] is done. Apart from reporting the amount of ]s and the ] level, the ] also measure the size of the red blood cells, which is an important tool in distinguishing between the causes. | |||
| ⚫ | Normocytic anemia can be caused by acute blood loss, chronic disease or failure to produce enough red blood cells |
||
| Occasionally, other tests are required to further distinguish the cause for anemia. These are discussed with the differential diagnosis (below). The doctor may also decide to take some other screening blood tests that might identify the cause of fatigue; ] levels, ], ], ] tests and ]s may be part of such a workup. | |||
| ⚫ | ] (bone marrow failure) is anemia caused by the inability of the ] to produce blood cells. Aplastic anemias are much rarer than dietary deficiency or genetic defect anemias. | ||
| ==Differential diagnosis== | |||
| ⚫ | ===Microcytic |
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| ⚫ | Anemia is classified by the size of the red blood cells; this is either done automatically or on microscopic examination of a peripheral blood smear. If the cells are smaller than normal, the anemia is said to be ''microcytic''; if they are normal size, ''normocytic''; and if they are larger than normal, the anemia is classified as ''macrocytic''. Other characteristics visible on the peripheral smear may provide valuable clues about a more specific diagnosis; for example, abnormal ]s may point to a cause in the ]. | ||
| ⚫ | The most common type |
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| ⚫ | ===Microcytic anemia=== | ||
| Iron deficiency anemia is caused when the dietary intake or absorption of ] is insufficient (Hemoglobin contains iron). In the United States, 20% of all women of childbearing age have iron deficiency anemia, compared with only 2% of adult men. The principal cause of iron deficiency anemia in premenopausal women is blood lost during ]. | |||
| ⚫ | The most common type of anemia overall is ]. Much rarer causes (apart from communities where these conditions are prevalent)are ] such as ] and ]. | ||
| ''Iron deficiency anemia'' is caused when the dietary intake or absorption of ] is insufficient. Iron is an essential part of hemoglobin, and low iron levels result in decreased incorporation of hemoglobin into red cells. In the United States, 20% of all women of childbearing age have iron deficiency anemia, compared with only 2% of adult men. The principal cause of iron deficiency anemia in premenopausal women is blood lost during ]. Studies have shown that iron deficiency without anemia causes poor school performance and lower ] in teenage girls. In older patients, iron deficiency anemia of often due to bleeding lesions of the ]; ]ing, ] and ] are often performed to identify bleeding lesions, which can be ]. | |||
| Iron deficiency anemia is the final stage of ]. When the body has sufficient iron to meet its needs (functional iron), the remainder is stored for later use in the ], ], and ]. Iron deficiency ranges from iron depletion, which yields little physiological damage, to iron deficiency anemia, which can affect the function of numerous organ systems. Iron depletion causes the amount of stored iron to be reduced, but has no affect on the functional iron. However, a person with no stored iron has no reserves to use if the body requires more iron. In essence, the amount of iron absorbed by the body is not adequate for growth and development or to replace the amount lost. | |||
| ⚫ | ===Normocytic anaemia=== | ||
| Studies have shown that iron deficiency without anemia causes poor school performance and lower ] in teenage girls. | |||
| ⚫ | Normocytic anemia can be caused by acute ], chronic disease ("anemia of chronic disease") or failure to produce enough red blood cells (as opposed to hemoglobin, which causes microcytic anemia). ] or ] cause normocytic anemia; in renal failure this is due to decreased production of the hormone ]. | ||
| Certain hormonal deficiencies, like ] (]), can cause normocytic anemia. Lastly, ''sideroblastic anemia'' is caused by abnormal production of red blood cells as part of ], which can evolve into ] (especially ]). | |||
| ===Fanconi Anemia=== | |||
| ⚫ | ] (bone marrow failure) is anemia caused by the inability of the ] to produce blood cells. Aplastic anemias are much rarer than dietary deficiency or genetic defect anemias, and progess rapidly. | ||
| Fanconi anemia (FA) is a rare genetic disease that affects children and adults from all ethnic backgrounds. Approximately 1,000 persons worldwide presently suffer from the disease. | |||
| ⚫ | ===Macrocytic anaemia=== | ||
| The overarching medical challenge that Fanconi patients face is a failure of their bone marrow to produce blood cells. In addition, Fanconi patients normally are born with a variety of birth defects. For instance, 90% of the Jewish children born with Fanconi's have no thumbs. A good number of Fanconi patients have kidney problems, trouble with their eyes, developmental retardation and other serious defects. | |||
| * The most common cause of macrocytic anemia is a deficiency of either ] or ] (or both) due either to inadequate intake or ]. ] is an ] condition where the body lacks ], required to absorb vitamin B12 from food. | |||
| * ] can cause macrocytic anemia. | |||
| Because of the failure of the components of the blood - white and red blood cells and platelets - the body cannot successfully combat infection, fatigue or spontaneous hemorrhage or bleeding. Bone marrow transplantation is the accepted treatment to repair the hematological problems associated with FA. Patients face an increased risk of acquiring cancer and other serious health problems throughout their lifetime. | |||
| * ] is a seperate constellation of symptoms (also featuring ] and elevated ] levels) with numerous potential causes. It can be ], ] and mechanical (e.g. ]). | |||
| ⚫ | The treatment for vitamin B12-deficient macrocytic anemia was first devised by ] who bled dogs to make them anemic and then fed them various substances to see what (if anything) would make them healthy again. He discovered that ingesting large amounts of liver seemed to cure the disease. ] and ] then set about to chemically isolate the curative substance and ultimately were able to isolate the ] from the liver. For this, all three shared the ] ]. | ||
| ==Classification based on the cause of the anemia== | |||
| ==Specific anemias== | |||
| The other major classification type for anaemia is based on the cause of the anaemia. There are three broad subcategories in this class which are: | |||
| * ] - a hereditary disease featuring ] and various other abnormalities | |||
| # problems with production of red blood cells (]) | |||
| # problems with red blood cell function | |||
| # excessive destruction of existing red blood cells (]) | |||
| ] | ] | ||
Revision as of 09:15, 18 June 2004
- This article discusses anemia, the medical condition. For the fern genus, see Anemia (fern).
Anemia (AE) or anaemia (BE) is a reduced ability of blood to transfer oxygen to the tissues due to a shortage in red blood cells or abnormalities in their function. Hemoglobin (the oxygen-carrying protein in the red blood cells) has to be present to ensure adequate oxygenation of all body tissues.
Anemia is the most common disorder of the blood. There are several kinds of anemia, produced by a variety of underlying causes. Anemia is classified by the size of the red blood cell: decreased (microcytic), normal (normocytic) or enlarged (macrocytic or megaloblastic).
Signs and symptoms
Anemia goes undetected in many people, and symptoms can be vague. Most commonly, a feeling of weakness or fatigue is reported. Shortness of breath is reported in more severe cases. Very severe anemia prompts a compensatory response where cardiac output is markedly increased, leading to palpitations and sweatiness; this process can lead to heart failure in elderly people.
Pallor (pale skin and mucosal linings) is only notable in cases of severe anemia, and is therefore not a reliable sign.
Diagnosis
The only way to diagnose anemia is with a blood test. Generally, a full blood count is done. Apart from reporting the amount of red blood cells and the hemoglobin level, the automatic counters also measure the size of the red blood cells, which is an important tool in distinguishing between the causes.
Occasionally, other tests are required to further distinguish the cause for anemia. These are discussed with the differential diagnosis (below). The doctor may also decide to take some other screening blood tests that might identify the cause of fatigue; glucose levels, ESR, ferritin, renal function tests and electrolytes may be part of such a workup.
Differential diagnosis
Anemia is classified by the size of the red blood cells; this is either done automatically or on microscopic examination of a peripheral blood smear. If the cells are smaller than normal, the anemia is said to be microcytic; if they are normal size, normocytic; and if they are larger than normal, the anemia is classified as macrocytic. Other characteristics visible on the peripheral smear may provide valuable clues about a more specific diagnosis; for example, abnormal white blood cells may point to a cause in the bone marrow.
Microcytic anemia
The most common type of anemia overall is iron deficiency anemia. Much rarer causes (apart from communities where these conditions are prevalent)are hemoglobinopathies such as sickle cell anaemia and thalassemia.
Iron deficiency anemia is caused when the dietary intake or absorption of iron is insufficient. Iron is an essential part of hemoglobin, and low iron levels result in decreased incorporation of hemoglobin into red cells. In the United States, 20% of all women of childbearing age have iron deficiency anemia, compared with only 2% of adult men. The principal cause of iron deficiency anemia in premenopausal women is blood lost during menses. Studies have shown that iron deficiency without anemia causes poor school performance and lower IQ in teenage girls. In older patients, iron deficiency anemia of often due to bleeding lesions of the gastrointestinal tract; fecal occult blood testing, upper and lower endoscopy are often performed to identify bleeding lesions, which can be malignant.
Normocytic anaemia
Normocytic anemia can be caused by acute blood loss, chronic disease ("anemia of chronic disease") or failure to produce enough red blood cells (as opposed to hemoglobin, which causes microcytic anemia). Chronic renal failure or liver failure cause normocytic anemia; in renal failure this is due to decreased production of the hormone erythropoietin.
Certain hormonal deficiencies, like testosterone deficiency (hypogonadism), can cause normocytic anemia. Lastly, sideroblastic anemia is caused by abnormal production of red blood cells as part of myelodysplastic syndrome, which can evolve into hematological malignancies (especially acute myelogenous leukemia).
Aplastic anemia (bone marrow failure) is anemia caused by the inability of the bone marrow to produce blood cells. Aplastic anemias are much rarer than dietary deficiency or genetic defect anemias, and progess rapidly.
Macrocytic anaemia
- The most common cause of macrocytic anemia is a deficiency of either vitamin B12 or folic acid (or both) due either to inadequate intake or insufficient absorption. Pernicious anemia is an autoimmune condition where the body lacks intrinsic factor, required to absorb vitamin B12 from food.
- Alcoholism can cause macrocytic anemia.
- Hemolytic anemia is a seperate constellation of symptoms (also featuring jaundice and elevated LDH levels) with numerous potential causes. It can be autoimmune, hereditary and mechanical (e.g. heart surgery).
The treatment for vitamin B12-deficient macrocytic anemia was first devised by William P. Murphy who bled dogs to make them anemic and then fed them various substances to see what (if anything) would make them healthy again. He discovered that ingesting large amounts of liver seemed to cure the disease. George R. Minot and George H. Whipple then set about to chemically isolate the curative substance and ultimately were able to isolate the vitamin B12 from the liver. For this, all three shared the 1934 Nobel Prize in Medicine.
Specific anemias
- Fanconi anemia - a hereditary disease featuring aplastic anemia and various other abnormalities
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