Pernicious Anemia (Vitamin B-12 Deficiency) (cont.)
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Pernicious Anemia Causes
The decreased absorption of vitamin B-12 from the gastrointestinal tract in pernicious anemia is believed to result from an autoimmune process in which the body's immune system attacks the lining of the stomach. Antibodies are produced against intrinsic factor (IF), a protein made in the stomach that is necessary for the absorption of vitamin B-12. Normally, vitamin B-12 binds to intrinsic factor in the stomach, and this facilitates its absorption later when digestive products pass through the small intestine. The autoimmune process attacks the IF protein and lowers IF levels in stomach secretions. An autoimmune process directed at the stomach lining cells also occurs and results in a chronic form of stomach inflammation (gastritis) known as chronic atrophic gastritis.
Pernicious anemia is most common in Caucasian persons of northern European ancestry than in other racial groups. In this population, 10-20 cases per 100,000 persons are diagnosed each year. Pernicious anemia may occur in association with other autoimmune diseases such as autoimmune thyroid disease and vitiligo.
While pernicious anemia is defined as anemia resulting from inadequate absorption of vitamin B-12 from the gastrointestinal tract due to the autoimmune process described above, other causes of vitamin B-12 deficiency can also produce the characteristic signs and symptoms of pernicious anemia. Other potential causes of vitamin B-12 deficiency include surgical removal of the stomach or a portion of the stomach (gastrectomy), other gastrointestinal diseases such as celiac disease or Crohn's disease, infection, and poor nutrition.
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