Pernicious Anemia

A megaloblastic anemia, pernicious anemia is characterized by decreased gastric production of hydrochloric acid and deficiency of intrinsic factor (IF), 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, gastric, and intestinal abnormalities. Untreated pernicious anemia may lead to permanent neurologic disability and death.

Pernicious anemia primarily affects people of northern European ancestry; in the United States, it's most common in New England and the Great Lakes region because of ethnic concentrations. It's rare in children, blacks, and Asians. Onset typically occurs between the ages of 50 and 60; incidence rises with increasing age.

Causes

Familial incidence of pernicious anemia suggests a genetic predisposition. Significantly higher incidence in patients with immunologically related diseases, such as thyroiditis, myxedema, and Graves' disease, seems to support a widely held theory that an inherited autoimmune response causes gastric mucosal atrophy and, therefore, deficiency of hydrochloric acid and IF.

Deficiency of lF impairs vitamin B12 absorption. The resultant vitamin B12-deficiency irihibits cell growth, particularly of red blood cells (RBCs), leading to insufficient and deformed RBCs with poor oxygen-carrying capacity. It also impairs myelin formation, causing
neurologic damage. Iatrogenic induction can follow partial gastrectomy.

Signs and symptoms

The following are the most common symptoms of megaloblastic anemia. However, each child may experience symptoms differently. Symptoms may include:

• abnormal paleness or lack of color of the skin
• decreased appetite
• irritability
• lack of energy or tiring easily (fatigue)
• diarrhea
• difficulty walking
• numbness or tingling in hands and feet
• smooth and tender tongue
• weak muscles

The symptoms of megaloblastic anemia may resemble other blood conditions or medical problems. Always consult your child's physician for a diagnosis.

Diagnosis

A positive family history, typical ethnic heritage, and results of blood studies, bone marrow aspiration, gastric analysis, and the Schilling test establish the diagnosis of pernicious anemia. 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, or drug therapy.

Treatment

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.

Prognosis

Prognosis is generally good for patients with pernicious anemia. Many of the symptoms improve within just a few days of beginning treatment, although some of the nervous system symptoms may take up to 18 months to improve. Occasionally, when diagnosis and treatment have been delayed for a long time, some of the nervous system symptoms may be permanent.

Because an increased risk of stomach cancer has been noted in patients with pernicious anemia, careful monitoring is necessary, even when all the symptoms of the original disorder have improved.

Prevention

Pernicious anemia is not preventable, but with early detection and treatment of vitamin B12 deficiency, complications are readily controlled.