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Anemia (American English) or anaemia (Commonwealth English),
which literally means "without blood," is
a lack of red blood cells and/or hemoglobin.
Anemia results in a reduced ability of blood to transfer oxygen to the
tissues. Hemoglobin (the oxygen-carrying protein in the red blood cells) has to
be present to ensure adequate oxygenation of all body tissues and organs.
The three main causes of anemia include excessive blood loss (hemorrhage),
excessive red blood cell destruction (hemolysis) or deficient red blood cell
production.
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 according to the size of the red blood cell: decreased (microcytic),
normal (normocytic) or enlarged (macrocytic or megaloblastic).
Signs and Symptoms of Anemia
Anemia symptoms go undetected in many people, as symptoms can be
vague. Most commonly, a feeling of weakness or fatigue is reported. Shortness of
breath is reported in more severe cases of anemia. 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 of Anemia
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 of anemia. 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 of Anemia
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. The size is reflected in the mean corpuscular volume (MCV). If the cells
are smaller than normal (under 80 fl), the anemia is said to be microcytic; if
they are normal size (80-100 fl), normocytic; and if they are larger than normal
(over 100 fl), 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, which is most often microcytic. 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.
Iron deficiency is the most prevalent deficiency state on a
worldwide basis. Iron deficiency affects women from different cultures and
ethnicities. In countries where meat consumption is not as common, iron
deficiency anemia is six to eight times more prevalent than in North America and
Europe. This is due to the importance of meat in the diets of North Americans
and Europeans.
- Normocytic
Anemia
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 progress rapidly.
- Macrocytic
Anemia
- The most common cause of macrocytic anemia is megaloblastic anemia due to a deficiency of either vitamin B12 or folic acid (or both) due
either to inadequate intake or insufficient absorption. Folate deficiency
normally does not produce neurological symptoms, while B12 deficiency does.
Pernicious
anemia is an autoimmune condition where the body lacks intrinsic
factor, required to absorb vitamin B12 from food.
- Alcoholism can cause macrocytic anemia.
- Drugs that inhibit DNA replication, such as methotrexate,
can also cause macrocytic anemia. This is the most common etiology in
nonalcoholic patients.
The treatment for vitamin B12-deficient macrocytic and
pernicious anemias was first devised by William 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 Minot and George 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
It is recommended that Transfer
Factor to be used in autoimmune conditions.
Transfer Factor Plus is generally preferred for
conditions caused by infection. Transfer Factors
suppress over acting immune system
to ease autoimmune conditions.
Anemia During Pregnancy
Anemia affects 20% of all females of childbearing age in the
United States. Because of the subtleness of the symptoms, women are often
unaware that they have this disorder, as they attribute the symptoms to the
stresses of their daily lives. Possible problems for the fetus include increased
risk of growth retardation, prematurity, intrauterine death, rupture of the
amnion and infection.
During pregnancy, women should be especially aware of the
symptoms of anemia, as an adult female loses an average of two milligrams of
iron daily. Therefore, she must intake a similar quantity of iron in order to
make up for this loss. Additionally, a woman loses approximately 500 milligrams
of iron with each pregnancy, compared to a loss of 4-100 milligrams of iron with
each period. Possible consequences for the mother include
cardiovascular
symptoms, reduces physical and mental performance, reduced
immune function,
tiredness, reduced peripartal blood reserves and increased need for blood
transfusion in the postpartum period.
Diet and Anemia
Consumption of food rich in iron is essential to prevention of
iron deficiency anemia. These foods include red meat; green, leafy
vegetables; dried beans; dried apricots, prunes, raisins, and other dried
fruits; almonds; seaweeds; parsley; whole grains; and yams.
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