Which type of anemia is associated with low levels of intrinsic factor?

• A. Sickle cell anemia
• B. Iron deficiency anemia
• C. Pernicious anemia
• D. Aplastic anemia

Answer: (C)

Intrinsic factor is a glycoprotein produced by gastric parietal cells and is essential for absorbing vitamin B12 in the terminal ileum. When intrinsic factor levels are low, vitamin B12 cannot be absorbed efficiently, causing a vitamin B12 deficiency. This leads to impaired DNA synthesis in red blood cell precursors, producing a megaloblastic, normocytic to macrocytic anemia. Pernicious anemia specifically refers to autoimmune destruction or functional impairment of the gastric parietal cells (and loss of intrinsic factor production), so the body cannot absorb B12 even if intake is adequate.

In contrast, sickle cell anemia is a hemoglobinopathy causing hemolytic anemia, iron deficiency anemia stems from insufficient iron and results in microcytic anemia, and aplastic anemia results from bone marrow failure. None depend on intrinsic factor, which is why pernicious anemia is the one associated with low intrinsic factor.