Pernicious anemia is primarily caused by a deficiency of which factor?

Pernicious anemia is primarily caused by a deficiency of intrinsic factor, which is a glycoprotein produced by the stomach's parietal cells. Intrinsic factor is essential for the absorption of vitamin B12 in the intestine. Without sufficient intrinsic factor, the body cannot adequately absorb vitamin B12, leading to a deficiency of this crucial vitamin. Vitamin B12 is vital for red blood cell production and DNA synthesis; its lack results in the production of large, dysfunctional red blood cells, characteristic of pernicious anemia.

The other options address factors related to other types of anemia but are not applicable in the context of pernicious anemia itself. Iron deficiency, for instance, leads to iron deficiency anemia rather than pernicious anemia. Vitamin D and folic acid deficiencies could affect overall health but do not directly relate to the mechanism of pernicious anemia. Therefore, the focus on intrinsic factor highlights its specific and critical role in the pathophysiology of pernicious anemia.