Anemia is a medical condition in which the blood is low in normal red blood cells.

Pernicious anemia is one cause of vitamin B-12 deficiency anemia. It’s thought mainly to be caused by an autoimmune process that makes a person unable to produce a substance in the stomach called intrinsic factor.

This substance is needed to absorb dietary vitamin B-12 in the small intestine. Vitamin B-12 is a required nutrient that helps allow proper red blood cell production and function in the body.

Pernicious anemia is a rare condition, with a prevalence of 0.1 percent in the general population and 1.9 percent in people who are older than 60 years, according to a 2012 study in the Journal of Blood Medicine.

However, up to 50 percent of anemia from vitamin B-12 deficiency in adults is caused by pernicious anemia.

This type of anemia is called “pernicious” because it was once considered a deadly disease. This was due to the lack of available treatment.

Today, though, the disease is relatively easy to treat with vitamin B-12 injections or possibly even oral supplementation. However, if left untreated, vitamin B-12 deficiency due to any cause can lead to severe complications.

The progression of pernicious anemia is typically slow. It may be difficult to recognize the symptoms because you may have become used to not feeling well.

Common symptoms include:

In more severe or prolonged cases of vitamin B-12 deficiency, including that due to pernicious anemia, people may have neurological symptoms. These can include:

Other symptoms of vitamin B-12 deficiency, including that due to pernicious anemia, include:

Lack of vitamin B-12 in the diet

People with anemia have low levels of normal red blood cells (RBCs). Vitamin B-12 plays a role in creating RBCs, so the body requires an adequate intake of vitamin B-12. Vitamin B-12 is found in:

  • meat
  • poultry
  • shellfish
  • eggs
  • dairy products
  • fortified soy, nut, and rice milks
  • nutritional supplements

Lack of intrinsic factor in the body

Your body also needs a type of protein called intrinsic factor (IF) to absorb vitamin B-12. IF is a protein produced by the parietal cells in the stomach.

After you consume vitamin B-12, it travels to your stomach where IF binds to it. The two are then absorbed in the last part of your small intestine.

In most cases of pernicious anemia, the body’s immune system attacks and destroys the cells, known as parietal cells, that produce IF in the stomach.

If these cells are destroyed, the stomach can’t make IF and the small intestine can’t absorb vitamin B-12 from in the diet, including from foods such as those listed above.

Small intestinal conditions

Diseases within the small intestine can cause deficiency of vitamin B-12 deficiency. These can include celiac disease, Crohn’s disease, or HIV.

If one has the ileum portion of the small intestine surgically removed, vitamin B-12 deficiency can also occur.

Disruption within the normal flora bacteria of the small intestine may also lead to vitamin B-12 deficiency. Antibiotics may cause a deficiency of bacteria needed to maintain proper intestinal absorption.

Other people may have too many small intestinal bacteria that cause malabsorption and a deficiency of vitamin B-12, as well.

Other vitamin B-12 deficiencies, such as that caused by poor dietary intake, are often confused with pernicious anemia.

Pernicious anemia is mainly thought to be an autoimmune disorder that hurts the parietal cells in the stomach. It results in a lack of IF production and poor B-12 absorption.

However, pernicious anemia may also have a genetic component to it as well, potentially running in families. There are also children with pernicious anemia who are born with a genetic defect that prevents them from making IF.

Pernicious anemia and anemia due to small intestinal malabsorption can be treated with an intramuscular B-12 injection by your physician. High dose oral vitamin B-12 supplementation may be an effective option for some people with pernicious anemia, as well.

In people with vitamin B-12 deficiency anemia where the body can absorb B-12, oral vitamin B-12 supplementation and diet adjustments may be an effective treatment.

Some individuals are more likely than others to develop pernicious anemia. Risk factors include:

  • having a family history of the disease
  • being of Northern European or Scandinavian descent
  • having type 1 diabetes mellitus, an autoimmune condition, or certain intestinal diseases such as Crohn’s disease
  • having had part of your stomach removed
  • being 60 years or older

Your risk of developing pernicious anemia also increases as you age.

Your doctor will usually need to do several tests to diagnose you with pernicious anemia. These include:

  • Complete blood count. This test can screen for an anemia in general by looking such things as hemoglobin and hematocrit levels.
  • Vitamin B-12 level. If vitamin B-12 deficiency is suspected as the cause of your anemia, your doctor can assess your vitamin B-12 level through this blood test. A lower than normal level indicates a deficiency.
  • IF and parietal cell antibodies. The blood is tested for antibodies against IF and the stomach’s parietal cells.

In a healthy immune system, antibodies are responsible for finding bacteria or viruses. They then mark the invading germs for destruction.

In an autoimmune disease such as pernicious anemia, the body’s immune system stops distinguishing between diseased and healthy tissue. In this case, autoantibodies destroy the stomachs cells that make IF.

The treatment for pernicious anemia is a two-part process. Your doctor will treat any existing vitamin B-12 deficiency.

Treatment of pernicious anemia usually consists of:

  • vitamin B-12 injections that are followed closely over time
  • following the blood level of vitamin B-12 over the course of therapy
  • making adjustments accordingly in vitamin B-12 dosing

Vitamin B-12 injections can be given daily or weekly until the B-12 levels return to normal (or close to normal). During the first few weeks of treatment, your doctor may recommend limiting physical activity.

After your vitamin B-12 levels are normal, you may only need to get the shot once per month. You may be able to administer the shots yourself or have someone else give them to you at home to save you trips to the doctor.

After your B-12 level is normal, your doctor may recommend you take oral doses of B-12 supplements instead of the injection.

However, depending on how deficient you are in intrinsic factor, where you then may have poor intestinal absorption of vitamin B-12 due to this, you may require vitamin B-12 injections as your sole treatment of pernicious anemia.

Your doctor will likely want to see you on a long-term basis. This will help them identify possible serious effects of pernicious anemia.

A dangerous potential complication is gastric cancer. They can monitor you for symptoms of cancer at regular visits and through imaging and biopsies, if needed.

Other potential complications of pernicious anemia include:

These complications most often stem from long-lasting pernicious anemia. They can be permanent.

Many people with pernicious anemia require lifelong treatment and monitoring. This can help prevent long-term damage from setting in to different body systems.

Talk to your doctor if you think you may have symptoms of pernicious anemia. Early diagnosis, treatment, and close monitoring are important for preventing any future problems.