Anemia

This article discusses the medical condition. For the fern genus, see Anemia (fern)

Anemia (American English) or anaemia (Commonwealth English), which literally means "without blood," is a deficiency of red blood cells and/or hemoglobin. This 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 classes of anemia include excessive blood loss (acutely such as a hemorrhage or chronically through low-volume loss), excessive red blood cell destruction (hemolysis) or deficient red blood cell production. In menstruating women, dietary iron deficiency is a common cause of 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

Anemia goes undetected in many people, and symptoms can be vague. Most commonly, people with anemia report a feeling of weakness or fatigue. People with more severe anemia sometimes report shortness of breath. Very severe anemia prompts the body to compensate by markedly increasing cardiac output, 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 definitively diagnose most cases of anemia is with a blood test. Generally, clinicians order a full blood count. Apart from reporting the number of red blood cells and the hemoglobin level, the automatic counters also measure the size of the red blood cells by flow cytometry, which is an important tool in distinguishing between the causes of anemia. A visual examination of a blood smear can also be helpful in some cases, and is sometimes a necessity in regions of the world where automated analysis is less accessible.

In modern counters, 4 parameters (RBC Count, hemoglobin concentration, MCV and RDW) are measured, allowing others (hematocrit, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration) to be calculated, and compared to values adjusted for age and sex.

When the cause is not obvious, clinicians use other tests to further distinguish the cause for anemia. These are discussed with the differential diagnosis, below. A clinician may also decide to order other screening blood tests that might identify the cause of fatigue; serum glucose, ESR, ferritin, serum iron, RBC folate level, serum vitamin B12, renal function tests (e.g. serum creatinine) and electrolytes may be part of such a workup.

Differential diagnosis

Anemia is classified by the size of 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

• iron deficiency anemia is the most common type of anemia overall, and it is often microcytic. 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 blood 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 is often due to bleeding lesions of the gastrointestinal tract; fecal occult blood testing, upper endoscopy 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.
• hemoglobinopathies -- much rarer (apart from communities where these conditions are prevalent)
  • sickle-cell disease
  • thalassemia

Microcytic anemia is primarily a result of hemoglobin synthesis failure/insufficieny, which could be caused by several etiologies:

• Heme synthesis defect
  • Iron deficiency
  • Anemia of Chronic Disorders (which, sometimes, is grouped into normocytic anemia)
• Globin synthesis defect
  • alpha-, and beta-thalassemia
  • HbE syndrome
  • HbC syndrome
  • and various other unstable hemoglobin diseases
• Sideroblastic defect
  • Hereditary Sideroblastic anemia
  • Acquired Sideroblastic anemia
  • Reversible Sideroblastic anemia

Normocytic anemia

• acute blood loss
• anemia of chronic disease
• aplastic anemia (bone marrow failure) is anemia caused by the inability of the bone marrow to produce red blood cells (as opposed to failure to produce enough hemoglobin, which causes microcytic anemia) . Aplastic anemias are much rarer than dietary deficiency or genetic defect anemias, and progess rapidly.
• chronic renal failure -- due to decreased production of the hormone erythropoietin
• liver failure
• testosterone deficiency (hypogonadism) and other certain hormonal deficiencies
• myelodysplastic syndrome causing abnormal production of red blood cells, which can evolve into hematological malignancies (especially acute myelogenous leukemia).

Macrocytic anemia

• 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. Megaloblastic anemia is the most common cause of macrocytic anemia.
• Pernicious anemia is an autoimmune condition where the body lacks intrinsic factor, required to absorb vitamin B12 from food.
• Alcoholism
• methotrexate, and other drugs that inhibit DNA replication. This is the most common etiology in nonalcoholic patients.

Macrocytic anemia can be further divided into 'megaloblastic anemia' or 'non-megaloblastic macrocytic anemia'. The cause of megaloblastic anemia is primarily a failure of DNA synthesis with preserved RNA synthesis, which result in restricted cell division of the progenitor cells. The megaloblastic anemias often present with neutrophil hypersegmentation (6-10 lobes). The non-megaloblastic macrocytic anemias have different etiologies (i.e. there is unimpaired DNA synthesis,) which occur, for example in alcoholism.

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.

Dimorphic Anemia

Here there are 2 types of anemia simultaneously, e.g., Macrocytic Hypochromic, due to hookworm infestation leading to deficiency of both iron and vitamin B12 or folic acid [1] or following a blood transfusion.

Specific anemias

• Fanconi anemia is a hereditary disease featuring aplastic anemia and various other abnormalities

• Hemolytic anemia is a separate constellation of symptoms (also featuring jaundice and elevated LDH levels) with numerous potential causes. It can be autoimmune, immune, hereditary or mechanical (e.g. heart surgery). It can result (because of cell fragmentation) in a microcytic anemia, a normochromic anemia, or (because of premature release of immature red blood cells from the bone marrow), a macrocytic anemia.

• Hereditary spherocytosis is a hereditary disease that results in defects in the RBC cell membrane, causing the erythrocytes to be sequestered and destroyed by the spleen. This leads to a decrease in the number of circulating RBCs and, hence, anemia.

• Warm autoimmune hemolytic anemia is an anemia caused by autoimmune attack against red blood cells, primarily by IgM

Possible complications

Anemia diminishes the capability of individuals who are affected to perform physical labor. This is a result of one's muscles being forced to depend on anaerobic metabolism. The lack of iron associated with anemia can cause many complications, including hypoxemia, brittle or rigid fingernails, cold intolerance, impaired immune functioning, and possible behavioral disturbances in children. Hypoxemia resulting from anemia can worsen the cardio-pulmonary status of patients with pre-existing chronic pulmonary disease. Brittle or rigid fingernails may be a result of abnormal thinness of nails due to insufficient iron supply. Cold intolerance occurs in one in five patients with iron deficiency anemia, and becomes visible through numbness and tingling. Impaired immune functioning leading to increased likelihood of sickness is another possible complications. Finally, chronic anemia may result in behavioral disturbances in children as a direct result of impaired neurological development in infants, and reduced scholastic performance in children of school age. Behavioral disturbances may even surface as an attention deficit disorder.

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, reduced 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; however, the average adult has approximately nine years worth of B12 stored in the liver, and it would take four to five years of an iron-deficient diet to create iron-deficiency anemia from diet alone.

Iron-rich foods include red meat; green, leafy vegetables; dried beans; dried apricots, prunes, raisins, and other dried fruits; almonds; seaweeds; parsley; whole grains; and yams. In extreme cases of anemia, researchers recommend consumption of beef liver, lean meat, oysters, lamb or chicken, or iron drops may be introduced. Certain foods have been found to interfere with iron absorption in the gastrointestnal tract, and these foods should be avoided. They include tea, coffee, wheat bran, rhubarb, chocolate, soft drinks, red wine, ice cream, and candy bars (Bauer, 2). With the exception of milk and eggs, animal sources of iron provide iron with better bioavailability than vegetal sources (Scrimshaw).

Treatments for anemia

There are many different treatments for anemia, including monitoring food intake and iron supplementation. In severe cases of anemia, a blood transfusion may be necessary.

References

• Breymann, Christian. “Iron Deficiency and Anemia in Pregnancy: Modern Aspects of Diagnosis and Therapy.” Blood Cells, Molecules, and Diseases. Nov/Dec: 2002.
• Conrad, Marcel E. “Iron Deficiency Anemia.” EMedicine. 8 Dec. 2004.
• Raymond, Tina. “Anemia: Diagnosis, Treatment and Prevention.” Midwifery Today. 31 May 1999.
• Scrimshaw, Nevin. Iron deficiency. Scientific American Oct 1991 pp 46-52

Related topics

• Blood diseases
• Hematology

External links

• Iron Deficiency Anemia - emedicine.com
• Ambulatory Management of Common Forms of Anemia - American Academy of Family Physicians
• Anemia Lifeline