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Congenital Lack Of Intrinsic Factor

Congenital Lack Of Intrinsic Factor

Alternate Names

  • congenital pernicious anemia


Intrinsic factor is a protein made by the stomach that helps the body absorb vitamin B12. Some people are born without the ability to make this protein. When this occurs, it is called a congenital lack of intrinsic factor. Congenital means that a condition is present at birth.

What is going on in the body?

In most people, the stomach makes the intrinsic factor protein. This protein attaches to the vitamin B12 that is taken in with the diet. The protein allows the vitamin B12 to be absorbed through the intestines and into the bloodstream. Once the vitamin is in the bloodstream, the body is able to use it.
When children are born without the intrinsic factor protein, they develop vitamin B12 deficiency. This deficiency can cause low red blood cell counts, called anemia. The anemia that occurs in this condition is called pernicious anemia.


What are the causes and risks of the disease?

A congenital lack of intrinsic factor is thought to be inherited in most cases.


What can be done to prevent the disease?

There are no known ways to prevent a congenital lack of intrinsic factor.


How is the disease diagnosed?

A congenital lack of intrinsic factor may be suspected after the history and physical exam. A blood test called a complete blood count, or CBC, is done first. This test counts the number of cells in the blood and will show a low number of red blood cells if anemia is present. Next, a blood test called a vitamin B12 level is usually done, which measures the vitamin B12 level in the blood. A child with congenital lack of intrinsic factor has a low level of vitamin B12.
The diagnosis of congenital lack of intrinsic factor can be confirmed by a Schilling test, which uses radioactive vitamin B12 to measure the amount of vitamin B12 absorbed by the intestines.

Long Term Effects

What are the long-term effects of the disease?

Most children have no long-term effects if the congenital lack of intrinsic factor is diagnosed and treated promptly. If treatment is delayed, permanent damage to the nervous system may occur. This may include numbness, weakness, and cognitive impairments, or an impaired ability to think logically. This damage may not go away with treatment.

Other Risks

What are the risks to others?

A congenital lack of intrinsic factor is not contagious. However, it is usually inherited. Genetic counseling may be helpful to couples with a family history of the disorder.


What are the treatments for the disease?

Congenital lack of intrinsic factor is usually treated with injections of vitamin B12 into a muscle. An injection is usually needed once a month for life. Pill forms of vitamin B12 cannot be used because a person without intrinsic factor cannot absorb the vitamin from the intestines.

Side Effects

What are the side effects of the treatments?

Injections can cause soreness at the site of the needle stick.

After Treatment

What happens after treatment for the disease?

A person with congenital lack of intrinsic factor needs lifelong treatment. Most children grow up to be healthy and can lead normal lives with no restrictions. Further treatment may be needed if nervous system damage has occurred.


How is the disease monitored?

Monitoring is not usually needed unless nervous system damage is present. Any new or worsening symptoms should be reported to the healthcare provider.


Rudolph's Fundamentals of Pediatrics, 1998, Rudolph et al.

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