Anemia is a condition in which the body does not have enough healthy red blood cells. Red blood cells provide oxygen to body tissues. There are many types of anemia.

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

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

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 (IF), 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 the actual intrinsic factor protein or the cells in the lining of your stomach 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 they 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:

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

Certain diseases can also raise your risk. They include:

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

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

They can include:

• Desire to eat ice or other non-food things (pica)
• 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 a low vitamin B12 level 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

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 level
• Methylmalonic acid (MMA) level
• Vitamin B12 level
• Levels of antibodies against IF or the cells which make IF

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

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

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.

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.

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

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

A woman with low B12 levels may have a false positive Pap smear. This is because vitamin B12 deficiency affects the way certain cells (epithelial cells) in the cervix look.

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

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

Antony AC. Megaloblastic anemias. In: Hoffman R, Benz EJ Jr, Silberstein LE, et al., eds. Hematology: Basic Principles and Practice. 6th ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 37.