Pernicious anemia - also known as Addison's anemia - is a megaloblastic anemia characterized by decreased gastric production of hydrochloric acid and deficiency of intrinsic factor, a substance normally secreted by the parietal cells of the gastric mucosa that is essential for vitamin B12 absorption. The resulting deficiency of vitamin B12 causes serious neurologic, psychological, gastric, and intestinal abnormalities. Increasingly fragile cell membranes induce widespread destruction of red blood cells (RBCs), resulting in low hemoglobin levels.
In the United States, pernicious anemia is most common in New England and the Great Lakes region because of ethnic concentration. It's rare in children, Blacks, and Asians. Onset typically is between ages 50 and 60; incidence increases with advancing age.
Familial incidence of pernicious anemia suggests a genetic predisposition. This disorder is significantly more common in patients with immunologically related diseases, such as thyroiditis, myxedema, and Graves' disease.
An inherited autoimmune response may cause gastric mucosal atrophy and, consequently, decreases hydrochloric acid and intrinsic factor production. Intrinsic factor deficiency impairs vitamin B12 absorption. The resultant vitamin B12 deficiency inhibits the growth of all cells, particularly RBCs, leading to insufficient and deformed RBCs with poor oxygen-carrying capacity.
Pernicious anemia also impairs myelin formation. Initially, it affects the peripheral nerves but gradually it extends to the spinal cord, causing neurologic dysfunction.
Secondary pernicious anemia can result from partial removal of the stomach, which limits the amount of productive mucosa.
The following are the most common symptoms for pernicious anemia. However, each individual may experience symptoms differently. Symptoms may include:
The results of blood studies, bone marrow examination, gastric analysis, and the Schilling test establish the diagnosis. Laboratory screening must rule out other anemias with similar symptoms, such as folic acid deficiency anemia, because treatment differs. Diagnosis must also rule out vitamin B12 deficiency resulting from malabsorption due to GI disorders, gastric surgery, radiation therapy, or drug therapy.
Treatment of pernicious anemia requires the administration of lifelong injections of B12 . Vitamin B12 given by injection enters the bloodstream directly, and does not require intrinsic factor. At first, injections may need to be given several times a week, in order to build up adequate stores of the vitamin. After this, the injections can be given on a monthly basis. Other substances required for blood cell production may also need to be given, iron and vitamin C.
Pernicious anemia is not preventable, but with early detection and treatment of vitamin B12 deficiency, complications are readily controlled.
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