Pernicious anemia
A megaloblastic anemia, pernicious anemia (also called Addison’s 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’s essential for vitamin B12 absorption. The resulting vitamin B12 deficiency 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 that is where people of that ancestry are concentrated. It’s rare in children, Blacks, and Asians. Onset typically occurs between ages 50 and 60; incidence rises with increasing age.
Causes
Familial incidence of pernicious anemia suggests a genetic predisposition. A 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 IF impairs absorption of vitamin B12. The resultant vitamin B12 deficiency inhibits cell growth, particularly of red blood cells (RBCs), leading to insufficient and deformed RBCs with poor oxygen-carrying capacity. Vitamin B12 deficiency also impairs myelin formation, causing neurologic
damage. Iatrogenic induction of IF deficiency can follow partial gastrectomy.
damage. Iatrogenic induction of IF deficiency can follow partial gastrectomy.
Signs and symptoms
Characteristically, pernicious anemia has an insidious onset but eventually causes an unmistakable triad of symptoms: weakness, sore tongue, and numbness and tingling in the extremities. The lips, gums, and tongue appear markedly bloodless. Hemolysis-induced hyperbilirubinemia may cause faintly jaundiced sclera and pale to bright yellow skin. The patient may also become highly susceptible to infection, especially of the genitourinary tract.
GI signs and symptoms
Gastric mucosal atrophy and decreased hydrochloric acid production disturb digestion and lead to nausea, vomiting, anorexia, weight loss, flatulence, diarrhea, and constipation. Gingival bleeding and tongue inflammation may hinder eating and intensify anorexia.
Central nervous system signs and symptoms
Nerve demyelination caused by vitamin B12 deficiency initially affects the peripheral nerves but gradually extends to the spinal cord. Consequently, the neurologic effects of pernicious anemia include neuritis, weakness in the extremities, peripheral numbness and paresthesia, disturbed position sense, lack of coordination, ataxia, impaired fine finger movement, positive Babinski’s and Romberg’s signs, light-headedness, optic muscle atrophy, loss of bowel and bladder control, impotence (in males), and altered vision (diplopia, blurred vision), taste, and hearing (tinnitus).
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