Vitamin B12 deficiency is commonly due to lack of intrinsic factor in the gastric mucosa, impairing absorption, leading to which condition?

Vitamin B12 deficiency is commonly due to lack of intrinsic factor in the gastric mucosa, impairing absorption, leading to which condition?

• A. Pernicious anemia
• B. Iron-deficiency anemia
• C. Pancytopenia
• D. Thalassemia

Answer: (A)

Vitamin B12 absorption depends on intrinsic factor produced by gastric parietal cells. When intrinsic factor is lacking or neutralized, vitamin B12 cannot be absorbed in the terminal ileum, leading to deficiency. This deficiency disrupts DNA synthesis in rapidly dividing cells, especially in the bone marrow, causing megaloblastic, macrocytic anemia known as pernicious anemia. Pernicious anemia is the autoimmune form often due to autoimmune gastritis or anti-intrinsic factor antibodies, which explains why this condition arises from the loss of intrinsic factor. The other options don’t fit the mechanism: iron-deficiency anemia results from low iron and produces microcytic cells; pancytopenia is a general reduction of all blood cell lines often from marrow failure; thalassemia is a genetic disorder affecting hemoglobin synthesis.

Vitamin B12 absorption depends on intrinsic factor produced by gastric parietal cells. When intrinsic factor is lacking or neutralized, vitamin B12 cannot be absorbed in the terminal ileum, leading to deficiency. This deficiency disrupts DNA synthesis in rapidly dividing cells, especially in the bone marrow, causing megaloblastic, macrocytic anemia known as pernicious anemia. Pernicious anemia is the autoimmune form often due to autoimmune gastritis or anti-intrinsic factor antibodies, which explains why this condition arises from the loss of intrinsic factor.

The other options don’t fit the mechanism: iron-deficiency anemia results from low iron and produces microcytic cells; pancytopenia is a general reduction of all blood cell lines often from marrow failure; thalassemia is a genetic disorder affecting hemoglobin synthesis.