Pernicious Anemia: Vitamin B12 Deficiency

Anemia is a blood disorder in which the number of red blood cells or the amount of hemoglobin is lower than normal. With fewer red blood cells or hemoglobin, insufficient oxygen is delivered to the body 's cells.
Pernicious anemia is a type of anemia caused by a deficiency in vitamin B12. In pernicious anemia, the lack of vitamin B12 is due to the body 's inability to produce enough intrinsic factor, a protein necessary for the absorption of vitamin B12.
Pernicious anemia is a type of megaloblastic anemia. Megaloblastic anemia is defined as, "a blood disorder characterized by anemia, with red blood cells that are larger than normal, usually resulting from a deficiency of folic acid or of vitamin B12. " (U.S. National Library of Medicine)

Pernicious anemia by any other name . . .

Pernicious anemia is known by a number of other names, including:
  • macrocytic achylic anemia
  • congenital pernicious anemia
  • juvenile pernicious anemia
  • vitamin B12 deficiency (malabsorption).

Causes of Pernicious Anemia

A lack of intrinsic factora protein necessary for the absorption of vitamin B12is the cause of pernicious anemia. With inadequate amounts of intrinsic factor, the body is unable to absorb vitamin B12. Often, the lack of intrinsic factor is due to inflammation of the stomach lining or the removal of part or all of the stomach.

Other causes of vitamin B12 deficiency include:
  • poor nutrition
  • gastrointestinal disorders
  • drugs
  • infections.
Vitamin B12 is found naturally only in foods of animal origin (meats, dairy products and eggs), so vegans may be at risk for vitamin B12 deficiency. However, anemia due to vitamin B12 deficiency is a slow-developing disease, because the liver usually has a supply of vitamin B12 that can last for a few years.

Risk Factors of Pernicious Anemia

Since pernicious anemia is a slow-developing disease, it typically affects older people. Symptoms of the disease rarely appear before the age of 30, but younger people, even infants, can have the disease. Sixty is the average age of diagnosis for pernicious anemia.
People of Northern European descent seem to be at a higher risk of pernicious anemia, and more women than men develop the disease. Those with a family history of autoimmune endocrine disorders also seem to be at a higher risk of developing pernicious anemia.

Not Just the Blood

Vitamin B12 is vital for the formation of blood cells, but other cells in the body, such as nerve cells, require vitamin B12 for proper functioning.

Symptoms of Pernicious Anemia

Pernicious anemia takes a long time to develop, so symptoms may not appear for years. Often, neurological symptoms caused by a B12 deficiency in the nerve cells appear before any other signs of anemia. Symptoms of pernicious anemia include:
  • fatigue
  • weakness
  • nausea
  • weight loss
  • diarrhea
  • rapid heart rate
  • shortness of breath
  • tingling or numbness in the hands and feet
  • problems with the tongue (extra sensitive tongue)
  • irritability
  • personality changes (also known as "megaloblastic madness ").

Organs Affected by Pernicious Anemia

While pernicious anemia is a disorder of the blood, the condition affects all organs of the body. With a decreased number of red blood cells, less oxygen is delivered to each cell. And with less available oxygen, the organs in the body are unable to function efficiently.

Diagnosing Pernicious Anemia

Pernicious anemia is usually detected through blood tests. Once the anemia has been detected, additional blood tests are taken, and the patient is given a thorough physical examination.
One of the primary tests for pernicious anemia is the Schilling test. In the Schilling test, radioactive vitamin B12 is taken orally and an injection of nonradioactive vitamin B12 is given a few hours later. Samples of urine collected over the next 24 hours are examined to determine whether vitamin B12 was properly absorbed.

Interpreting Results of the Schilling Test

The ileum is the part of the small intestine responsible for the majority of vitamin B12 absorption. If absorption occurs normally, the ileum absorbs more vitamin B12 than the body needs. Some is stored in the liver, but much of the excess is excreted in the urine. If traces of radioactive vitamin B12 are found in the urine (normal values range from about 8 to 40 percent), then the body is properly absorbing vitamin B12.

Treating Pernicious Anemia

The primary form of treatment for pernicious anemia is a monthly vitamin B12 injection, but treatment depends on a multitude of factors, including the doctor 's recommendation, the patient 's personal preferences, the patient 's overall health and the severity of the disease.
The doctor may also recommend that the patient take dietary supplements of vitamin B12, since the intestine absorbs about one percent of the vitamin B12 even without the presence of intrinsic factor.
Dietary changes may also be suggested, where the patient eats more food rich in vitamin B12 and folic acid.
Foods rich in vitamin B12 include:
  • eggs
  • meat
  • milk
  • shellfish
Foods rich in folic acid are:
  • oranges
  • spinach
  • rice
  • barley
  • sprouts
  • soybeans
  • beans
  • peanuts
  • broccoli
  • asparagus
  • peas
  • green, leafy vegetables

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