Which vitamin deficiency is primarily responsible for Pernicious anemia?

Pernicious anemia is primarily caused by a deficiency in vitamin B12. This vitamin is essential for the proper formation of red blood cells and the maintenance of healthy nerve cells. In the case of pernicious anemia, the body either cannot properly absorb vitamin B12 due to a lack of intrinsic factor, a protein produced in the stomach that is necessary for B12 absorption, or there may be an autoimmune response that damages the cells responsible for producing intrinsic factor.

Without sufficient vitamin B12, the body cannot produce adequate amounts of hemoglobin, leading to larger-than-normal red blood cells unable to efficiently transport oxygen. This results in symptoms such as fatigue, weakness, and neurological issues due to the vitamin's role in myelin sheath formation around nerves.

The other vitamins, B1, B2, and B6, while important for various metabolic processes, do not play a direct role in the development of pernicious anemia or its characteristic symptoms. Each of these vitamins has distinct functions in the body, but they do not directly relate to the absorption or utilization of vitamin B12, which is central to the pathology of pernicious anemia.