Failure of vitamin B12 absorption occurs in pernicious anemia due to intrinsic factor (IF) deficiency and gastric achlorhydria

Failure of vitamin B12 absorption occurs in pernicious anemia due to intrinsic factor (IF) deficiency and gastric achlorhydria

Pernicious anemia is an autoimmune condition that results in the deficiency of intrinsic factor (IF), a protein produced by the parietal cells of the stomach. Intrinsic factor is crucial for the absorption of vitamin B12 in the small intestine.

The sequence of events leading to vitamin B12 deficiency in pernicious anemia is as follows:

  1. Intrinsic Factor Deficiency: In pernicious anemia, the immune system attacks and destroys the parietal cells of the stomach. These cells are responsible for producing intrinsic factor.
  2. Inability to Form B12-Intrinsic Factor Complex: Intrinsic factor binds to vitamin B12 in the stomach, forming a complex. This complex is necessary for the absorption of vitamin B12 in the later part of the small intestine, called the ileum.
  3. Impaired Absorption of B12: Without intrinsic factor, the formation of the B12-intrinsic factor complex is disrupted. As a result, vitamin B12 cannot be efficiently absorbed from the gastrointestinal tract.
  4. Vitamin B12 Deficiency: The lack of intrinsic factor and subsequent impaired absorption of vitamin B12 lead to a deficiency of this essential vitamin. Vitamin B12 is crucial for the synthesis of DNA, the functioning of the nervous system, and the production of red blood cells.

In addition to intrinsic factor deficiency, individuals with pernicious anemia often have gastric achlorhydria, a condition characterized by a lack of stomach acid (hydrochloric acid). This further contributes to impaired B12 absorption since stomach acid is needed to release vitamin B12 from dietary proteins, allowing it to bind to intrinsic factor.

To manage vitamin B12 deficiency in pernicious anemia, individuals typically require lifelong vitamin B12 supplementation, often administered through injections or high-dose oral supplements. Regular monitoring of vitamin B12 levels and clinical symptoms is important for ongoing management. It’s important for individuals with pernicious anemia to work closely with healthcare providers for proper diagnosis and management.