Definition

Pernicious anemia is a decrease in red blood cells that occurs when your intestines cannot properly absorb vitamin B12. 

See also:

  • Megaloblastic anemia
  • Anemia

Alternative Names

Macrocytic achylic anemia; Congenital pernicious anemia; Juvenile pernicious anemia; Vitamin B12 deficiency (malabsorption)

Causes, incidence, and risk factors

Pernicious anemia is a type of vitamin B12 anemia. The body needs vitamin B12 to make red blood cells. You get this vitamin from eating foods such as meat, poultry, shellfish, eggs, and dairy products.

A special protein, called intrinsic factor, helps your intestines absorb vitamin B12. This protein is released by cells in the stomach. When the stomach does not make enough intrinsic factor, the intestine cannot properly absorb vitamin B12.

Common causes of pernicious anemia include:

  • Weakened stomach lining (atrophic gastritis)
  • An autoimmune condition in which the body’s immune system attacks intrinsic factor protein or the cells that make it.

Very rarely, pernicious anemia is passed down through families. This is called congenital pernicious anemia. Babies with this type of anemia do not make enough intrinsic factor or cannot properly absorb vitamin B12 in the small intestine.

In adults, symptoms of pernicious anemia are usually not seen until after age 30. The average age of diagnosis is age 60.

You are more likely to get this disease if you:

  • Scandinavian or Northern European
  • Have a family history of the condition

Certain diseases can also raise your risk. They include:

  • Addison’s disease
  • Chronic thyroiditis
  • Graves disease
  • Hypoparathyroidism
  • Hypopituitarism
  • Myasthenia gravis
  • Secondary amenorrhea
  • Type 1 diabetes
  • Testicular dysfunction
  • Vitiligo

For information on other causes of low vitamin B12 levels, see: Anemia – B12 deficiency

Symptoms

Some people do not have symptoms. Symptoms may be mild.

They can include:

  • Diarrhea or constipation
  • Fatigue, lack of energy, or light-headedness when standing up or with exertion
  • Loss of appetite
  • Pale skin
  • Problems concentrating
  • Shortness of breath, mostly during exercise
  • Swollen, red tongue or bleeding gums

If you have low vitamin B12 levels for a long time, you can have nervous system damage. Symptoms can include:

  • Confusion
  • Depression
  • Loss of balance
  • Numbness and tingling in the hands and feet

Signs and tests

The doctor or nurse will perform a physical exam. Tests that may be done include:

  • Bone marrow examination (only needed if diagnosis is unclear)
  • Complete blood count (CBC)
  • Reticulocyte count
  • Schilling test
  • LDH
  • Methylmalonic acid (MMA) level
  • Vitamin B12 level

This list is not all-inclusive.

Pernicious anemia may also affect the results of the following tests:

  • Bilirubin
  • Cholesterol test
  • Gastrin
  • Leukocyte alkaline phosphatase
  • Peripheral smear
  • TIBC

 A woman with low B12 levels may have a false positive Pap smear. That’s because a vitamin B12 deficiency affects the cells certain cells, called epithelial cells, look.

Treatment

The goal of treatment is to increase your vitamin B12 levels.

  • Treatment involves a  shot of vitamin B12 once a month. Persons with severely low levels of B12 may need more shots in the beginning.
  • Some patients may also need to take vitamin B12 supplements by mouth. For some people, high-dose vitamin B12 tablets taken by mouth work well, and shots are not needed.
  • A certain type of vitamin B12 may be given through the nose.

Your doctor or nurse will also recommend eating a well-balanced diet.

Expectations (prognosis)

Patients usually do well with treatment.

It is important to start treatment early. Nerve damage can be permanent if treatment does not start within 6 months of symptoms.

Complications

People with pernicious anemia may have gastric polyps, and are more likely to develop gastric cancer and gastric carcinoid tumors.

Brain and nervous system problems may continue or be permanent if treatment is delayed.

Calling your health care provider

Call your health care provider if you have symptoms of vitamin B12 deficiency.

Prevention

There is no known way to prevent this type of vitamin B12 anemia. However, early detection and treatment can help reduce complications.

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