Pernicious anemia is caused by a lack of intrinsic factor or other causes, such as infections, surgery, medicines, or diet.
Intrinsic factor is a protein made in the stomach. It helps your body absorb vitamin B12. In some people, an autoimmune response causes a lack of intrinsic factor.
An autoimmune response occurs if the body’s immune system makes antibodies (proteins) that mistakenly attack and damage the body's tissues or cells.
In pernicious anemia, the body makes antibodies that attack and destroy the parietal (pa-RI-eh-tal) cells. These cells line the stomach and make intrinsic factor. Why this autoimmune response occurs isn't known.
As a result of this attack, the stomach stops making intrinsic factor. Without intrinsic factor, your body can't move vitamin B12 through the small intestine, where it's absorbed. This leads to vitamin B12 deficiency.
A lack of intrinsic factor also can occur if you've had part or all of your stomach surgically removed. This type of surgery reduces the number of parietal cells available to make intrinsic factor.
Rarely, children are born with an inherited disorder that prevents their bodies from making intrinsic factor. This disorder is called congenital pernicious anemia.
Pernicious anemia also has other causes, besides a lack of intrinsic factor. Malabsorption in the small intestine and a diet lacking vitamin B12 both can lead to pernicious anemia.
Sometimes pernicious anemia occurs because the body's small intestine can't properly absorb vitamin B12. This may be the result of:
Some people get pernicious anemia because they don't have enough vitamin B12 in their diets. This cause of pernicious anemia is less common than other causes.
Good food sources of vitamin B12 include:
Strict vegetarians who don't eat any animal or dairy products and don't take a vitamin B12 supplement are at risk for pernicious anemia.
Breastfed infants of strict vegetarian mothers also are at risk for pernicious anemia. These infants can develop anemia within months of being born. This is because they haven't had enough time to store vitamin B12 in their bodies. Doctors treat these infants with vitamin B12 supplements.
Other groups, such as the elderly and people who suffer from alcoholism, also may be at risk for pernicious anemia. These people may not get the proper nutrients in their diets.
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