Health Encyclopedia

Pernicious anemia

Definition

Pernicious anemia is a decrease in red blood cells that occurs when the body cannot properly absorb vitamin B12 from the gastrointestinal tract. Vitamin B12 is necessary for the formation of red blood cells.

Pernicious anemia is a type of megaloblastic anemia.

Alternative Names

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

Causes, incidence, and risk factors

Pernicious anemia is caused by a lack of intrinsic factor. Intrinsic factor is a protein produced by the stomach that helps the body absorb vitamin B12. When stomach does not have enough intrinsic factor, it cannot properly absorb the vitamin. Nerve and blood cells need vitamin B12 to function properly.

Very rarely, infants and children are born without the ability to produce enough intrinsic factor. Congenital (born with) pernicious anemia is inherited as an autosomal recessive disorder (you need the defective gene from each parent to get it). Most often, however, pernicious anemia and other forms of megaloblastic anemia in children result from other causes of vitamin B12 deficiency or other vitamin deficiencies.

Other causes of low levels of intrinsic factor (and thus of pernicious anemia) include atrophic gastric mucosa, autoimmunity against gastric parietal cells, and autoimmunity against intrinsic factor.

The onset of the disease is slow and may take decades. Although the congenital form occurs in children, pernicious anemia usually does not appear before age 30. The average age at diagnosis is 60.

Risk factors include:

Family history of the disease
Scandinavian or Northern European descent
History of autoimmune endocrine disorders, including type 1 diabetes, hypoparathyroidism, Addison's disease, hypopituitarism, testicular dysfunction, Graves disease, chronic thyroiditis, myasthenia gravis, secondary amenorrhea, and vitiligo

In addition to pernicious anemia, other causes of vitamin B12 deficiency include:

Certain drugs, including colchicine, neomycin, and para amino salicylic acid used for tuberculosis treatment
Gastrointestinal disease (stomach removal surgery, celiac disease, Crohn's disease)
Infection (intestinal parasites, bacterial overgrowth)
Metabolic disorders (methylmalonic aciduria, homocystinuria)
Nutritional problems (strict vegetarians without B12 supplementation, poor diet in infant, or poor nutrition during pregnancy)

Symptoms

Too little vitamin B12 gradually causes neurological problems. It is important to know that the neurological effects may be seen before anemia is diagnosed.

Symptoms may include:

Shortness of breath
Fatigue
Pallor
Rapid heart rate
Loss of appetite
Diarrhea
Tingling and numbness of hands and feet
Sore mouth
Unsteady gait, especially in the dark
Tongue problems
Impaired sense of smell
Bleeding gums
Positive Babinski's reflex
Loss of deep tendon reflexes
Personality changes, "megaloblastic madness"

Signs and tests

Tests that may used to diagnose or monitor pernicious anemia include:

Complete blood count
Bone marrow examination (only needed if diagnosis is unclear)
Measurement of serum holotranscobalamin II
Measurement of methylmalonic acid (MMA)
Reticulocyte count
Serum LDH
Schilling test
Vitamin B12 level

This disease may also alter the results of the following tests:

Bilirubin
Cholesterol test
Gastrin
Leukocyte alkaline phosphatase
Peripheral smear
TIBC

Vitamin B12 deficiency affects the appearance of all epithelial cells, therefore an untreated woman may have a false positive pap smear.

Treatment

Monthly vitamin B12 injections are prescribed to correct the vitamin B12 deficiency. This therapy corrects the anemia and may correct the neurological complications if taken soon enough.

Some doctors recommend that elderly patients with gastric atrophy take vitamin B12 supplements by mouth in addition to monthly injections.

There is also a preparation of vitamin B12 that may be given through the nose).

A well-balanced diet is essential to provide other elements for healthy blood cell development, such as folic acid, iron, and vitamin C.

Expectations (prognosis)

The outcome is usually excellent with treatment.

Complications

People with pernicious anemia may have gastric polyps and get gastric cancer and gastric carcinoid tumors twice as often than the normal population.

Persistent neurological defects may be present if treatment is delayed.

Calling your health care provider

Call your health care provider if symptoms suggestive of vitamin B12 deficiency develop.

Prevention

There is no known prevention. However, with early detection and treatment of vitamin B12 deficiency, complications can be controlled.

Review Date:8/27/2007
Reviewed By:Stephen Grund, M.D. Ph.D., Chief of Hematology/Oncology and Director of the George Bray Cancer Center at New Britain General Hospital, New Britain, CT. Review provided by VeriMed Healthcare Network.

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