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Pernicious anemia

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Pernicious anemia

Definition:

Pernicious anemia is caused by a lack of intrinsic factor, a substance needed to absorb vitamin B-12 from the gastrointestinal tract. Vitamin B-12 is necessary for the formation of red blood cells.

Anemia is a condition where red blood cells are not providing adequate oxygen to body tissues. There are many types and causes of anemia. (See the general article - anemia)

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Pernicious anemia is a type of megaloblastic anemia.

Alternative Names:

Macrocytic achylic anemia; Congenital pernicious anemia; Juvenile pernicious anemia; Vitamin B-12 deficiency (malabsorption)

Causes, incidence, and risk factors:

Intrinsic factor is a protein that helps the body absorb vitamin B-12. When stomach secretions do not have enough intrinsic factor, vitamin B-12 is not absorbed well. This results in pernicious anemia and other problems related to low levels of vitamin B-12.

Nerve and blood cells need vitamin B-12 to function properly, so deficiency can cause a wide variety of symptoms, including fatigue, shortness of breath, tingling sensations, difficulty walking, and diarrhea.

Other causes of low levels of intrinsic factor (and thus of pernicious anemia) include atrophic gastric mucosa, autoimmunity against gastric parietal cells, and autoimmunity against intrinsic factor.

Absence of intrinsic factor itself is the most common cause of vitamin B-12 deficiency. Intrinsic factor is produced by cells in the stomach. In adults, the inability to make intrinsic factor can be the result of chronic gastritis or the result of surgery to remove the stomach. The onset of the disease is slow and may take decades.

Very rarely, infants and children are born lacking the ability to produce effective intrinsic factor. This form of congenital (born with) pernicious anemia is inherited as an autosomal recessive disorder (you need a defective gene from each parent to get it). Most often, however, pernicious anemia and other forms of megaloblastic anemia in children results from other causes of vitamin B-12 deficiency or other vitamin deficiencies.