Pernicious anemia is caused by a deficiency of which nutrient due to loss of intrinsic factor?

• A. Vitamin B12
• B. Folic acid
• C. Iron
• D. Vitamin C

Answer: (A)

Pernicious anemia happens when intrinsic factor, the protein produced by stomach lining that is essential for absorbing vitamin B12 in the small intestine, is lost or blocked. Without intrinsic factor, vitamin B12 cannot be efficiently absorbed, leading to a deficiency that causes the characteristic megaloblastic anemia. Vitamin B12 is the nutrient whose lack creates this condition, whereas folic acid deficiency also causes megaloblastic anemia but is not caused by the loss of intrinsic factor. Iron deficiency leads to a different, typically microcytic anemia, and vitamin C deficiency causes scurvy rather than a primary vitamin deficiency related to intrinsic factor. So the nutrient involved here is vitamin B12.