What Causes Pernicious Anemia?
Pernicious anemia is caused by a lack of vitamin B12
in the body. The main reason for the vitamin B12 deficiency is the loss of
parietal (pa-RI-e-tal) cells in the lining of the stomach. These cells make
intrinsic factor, which helps the body absorb vitamin B12 in the small
intestine. In some people, the bodys immune system may attack and destroy
the parietal cells. Doctors dont know exactly why or how this happens, or
if the immune system produces antibodies in reaction to normally aging or dying
As a result of this immune system attack, the
stomach lining shrinks, and the parietal cells in the lining of the stomach
disappear. The stomach stops producing intrinsic factor. Over time, vitamin B12
Loss of intrinsic factor can also be due to removal
of the stomach lining in various kinds of stomach surgery. This surgery
includes removal of all or part of the stomach as well as stomach surgery for
There is also a rare inherited disorder in which
children are born without the ability to produce intrinsic factor.
Less common causes of pernicious anemia include a
diet low in vitamin B12, intestinal problems, and certain medicines.
Lack of Vitamin B12 in the Diet
People can develop pernicious anemia if they
dont get enough vitamin B12 in the foods that they eat. This condition
takes many years to develop because it takes time to use up the vitamin B12
already stored in the body.
Some people who are strict vegetarians can develop
pernicious anemia, especially if they do not eat meat, poultry, fish, eggs, or
dairy productsthe best food sources of vitamin B12. Breastfed
infants of strict vegetarian mothers can develop anemia in a short time because
they dont have enough vitamin B12 stored in their bodies. They can be
given vitamin B12 supplements to prevent this type of anemia.
Some people develop pernicious anemia because of a
poor diet due to conditions such as alcoholism or aging.
Disorders of the Small Intestine
Some intestinal problems can cause poor absorption
of vitamin B12. These problems include:
- An infection caused by parasites or an overgrowth
of bacteria in the intestine
- Celiac disease (also known as sprue), a genetic disorder that
makes a person unable to tolerate gluten
- Crohns disease, an inflammatory bowel disease
- Not enough stomach acid to digest fooda
problem that can occur in older adults
Long-term use of certain medicines may lead to
pernicious anemia. Examples of these are medicines that reduce acid in the
stomach and certain diabetes medicines (such as metformin, phenformin, and