Pernicious anemia (per-NISH-us uh-NEE-me-uh) is a condition in which the body can't make enough healthy red blood cells because it doesn't have enough vitamin B12.
Vitamin B12 is a nutrient found in certain foods. The body needs this nutrient to make healthy red blood cells and to keep its nervous system working properly.
People who have pernicious anemia can't absorb enough vitamin B12 from food due to a lack of intrinsic (in-TRIN-sik) factor, a protein made in the stomach. This leads to vitamin B12 deficiency.
Other conditions and factors also can cause vitamin B12 deficiency. Examples include infections, surgery, medicines, and diet. Technically, the term "pernicious anemia" refers to vitamin B12 deficiency due to lack of intrinsic factor. Often, vitamin B12 deficiency due to other causes also is called pernicious anemia.
Pernicious anemia is a type of anemia (a condition in which your body has a lower than normal number of red blood cells). In pernicious anemia, the body can't make enough healthy red blood cells because it doesn't have enough vitamin B12.
Without enough vitamin B12, your red blood cells don't divide normally and are too large. They may have trouble getting out of the bone marrow—a sponge-like tissue inside the bones where blood cells are made.
Without enough red blood cells to carry oxygen to your body, you may feel tired and weak. Severe or long-lasting pernicious anemia can damage the heart, brain, and other organs in the body.
Pernicious anemia also can cause other complications, such as nerve damage, neurological problems (such as memory loss), and digestive tract problems. People who have pernicious anemia also may be at higher risk for stomach cancer.
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