Pernicious anemia is associated with deficiency of which vitamin?

• A. Vitamin A
• B. Vitamin B12
• C. Vitamin C
• D. Vitamin D

Answer: (B)

Pernicious anemia occurs when the body cannot absorb vitamin B12 because intrinsic factor, produced by stomach parietal cells, is absent or dysfunctional. Without enough B12, red blood cell precursors can’t synthesize DNA properly, leading to enlarged, immature cells and a megaloblastic, or macrocytic, anemia. B12 is also needed for proper myelin maintenance, so deficiency can be associated with neurological symptoms as well. Because the problem in pernicious anemia is impaired absorption of vitamin B12 rather than a lack of dietary intake of other nutrients, the deficiency points to vitamin B12. The other vitamins listed cause different deficiency syndromes (A deficiency affects vision and skin, C deficiency causes scurvy, and D deficiency leads to bone problems) and are not linked to pernicious anemia.