Pernicious anemia causes
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Causes
Most commonly, the cause for impaired binding of vitamin B12 by intrinsic factor is autoimmune atrophic gastritis, in which autoantibodies are directed against parietal cells (resulting in their loss) as well as against the intrinsic factor itself (rendering it unable to bind vitamin B12). Less frequently, loss of parietal cells may simply be part of a widespread atrophic gastritis of non-autoimmune origin, such as that frequently occurring in elderly people affected with long-standing chronic gastritis of any cause (including Helicobacter pylori infection). Note that forms of vitamin B12 deficiency other than pernicious anaemia must be considered in the differential diagnosis of megaloblastic anaemia.
- The body needs vitamin B12 to make red blood cells. To provide vitamin B12 to your blood cells, you need to eat enough foods containing vitamin B12, such as meat, poultry, shellfish, eggs, and dairy products. To absorb vitamin B12, your body uses a special protein called intrinsic factor, which is released by cells in the stomach. The combination of vitamin B12 bound to intrinsic factor is absorbed in the last part of the small intestine.
When the stomach does not make enough intrinsic factor, the intestine cannot properly absorb vitamin B12.
- Very rarely, infants and children are born without the ability to produce enough intrinsic factor, or the ability to absorb the combination of intrinsic factor and vitamin B12 in the small intestine. Pernicious anemia that occurs at birth (congenital) is inherited. You need the defective gene from each parent to get it.
- Common causes of pernicious anemia include:
- Weakened stomach lining (atrophic gastritis)
- The body's immune system attacking the cells that make intrinsic factor (autoimmunity against gastric parietal cells) or intrinsic factor itself
- The disease begins slowly and may take decades to fully establish. Although the congenital form occurs in children, pernicious anemia usually does not appear before age 30 in adults. The average age at diagnosis is 60.