Pernicious Anemia - Pathophysiology

Pathophysiology

Vitamin B₁₂ cannot be produced by the human body, and must be obtained from the diet. Normally, dietary B₁₂ is absorbed by the body in the small bowel only when it is bound by the intrinsic factor (IF) produced by parietal cells of the gastric mucosa. Pernicious anemia is thought to occur when the body's immune system mistakenly targets the IF, with a loss of parietal cells. Insufficient IF results in insufficient absorption of the vitamin. Although the normal body stores three to five years' worth of B₁₂ in the liver, the usually undetected autoimmune activity in one's gut over a prolonged period of time leads to B₁₂ depletion and the resulting anemia. Inhibition of DNA synthesis in red blood cells results in the formation of large, fragile megaloblastic erythrocytes.