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What Is Pernicious Anemia?

Pernicious anemia (per-NISH-us uh-NEE-me-uh) is a condition in which the body does not make enough red blood cells due to a lack of vitamin B12 in the body. It usually occurs in people whose bodies have lost the ability to absorb vitamin B12 from food.


Pernicious anemia is one of many different types of anemia. Having anemia means you do not have enough healthy red blood cells. When a person has anemia, the blood cannot carry enough oxygen to the cells of the body. The most common symptom of anemia is feeling tired.

Pernicious Anemia

In pernicious anemia, the blood cells do not divide normally and are too large. They have trouble getting out of the bone marrow. The problem is due to a lack of vitamin B12 in the body. Vitamin B12 is one of the B vitamins; B vitamins are found in animal foods such as meat, fish, eggs, milk, and other dairy products. Vitamin B12 is necessary for the body to make red blood cells. It is also needed for the normal working of the nervous system.

People can develop low levels of this important vitamin in three main ways:

  • From the lack of a protein in the stomach that helps the body absorb vitamin B12. The protein is called intrinsic (in-TRIN-sik) factor. Intrinsic factor is made by special cells in the lining of the stomach. In some people, these cells are destroyed by the body’s immune system or as a result of stomach surgery. When this happens, intrinsic factor is not produced and vitamin B12 cannot be absorbed. This is the most common cause of vitamin B12 deficiency.
  • From not getting enough vitamin B12 in the diet. This can be the result of eating a strict vegetarian diet or a poor diet due to factors such as aging or alcoholism.
  • From certain intestinal disorders that interfere with the absorption of vitamin B12, such as Crohn’s disease and intestinal infections.

The condition was named “pernicious” anemia because it was often fatal in the years before the cause was discovered to be a lack of vitamin B12, and no specific treatments were available. Now it is easy to treat with vitamin B12 pills or injections. Pernicious anemia can be severe if it goes on for a long time without being treated. If it is not treated, it can cause permanent damage to the body. Pernicious anemia is especially common in older adults.

Effects of Pernicious Anemia on the Body

People who have pernicious anemia often feel tired and weak because the body is not getting enough oxygen. Over time, if untreated, this disease can cause serious problems for the heart, nerves, and other parts of the body.

Heart. In people with anemia, the heart has to work harder to pump blood to get enough oxygen to the body’s organs and tissues. This stress on the heart can cause heart murmurs (an extra or unusual sound heard during the heartbeat), fast or irregular heartbeats, an enlarged heart, or even heart failure.

A lack of vitamin B12 or folic acid (folate) can cause extra problems for the heart because it raises the level in the body of a chemical called homocysteine (ho-mo-SIS-teen). High levels of homocysteine add to the buildup of fatty deposits in blood vessels, which in turn can lead to heart attacks and strokes.

Nerves. A lack of vitamin B12 can damage nerve cells and cause problems such as tingling and numbness in hands and feet and problems with walking and balance. A vitamin B12 deficiency can cause changes in taste, smell, and vision. Finally, it can cause mental changes, including memory loss and confusion.

Digestive tract. A lack of vitamin B12 may change the surface of the tongue and shrink or thin the stomach lining. Any changes that occur in the stomach can put a person at risk for stomach cancer.


Pernicious anemia is usually easy to treat with vitamin B12 pills or shots, although some people develop permanent nerve damage before they find out they have the disease and get treatment. Since pernicious anemia does increase the risk of developing stomach cancer, doctors may do periodic cancer tests to check for it. Overall, however, people with pernicious anemia who get proper lifelong treatment can have a normal lifespan.

May 2006

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