Pernicious anemia is a deficiency of which vitamin?

• A. Vitamin B-9
• B. Vitamin B-6
• C. Vitamin B-12
• D. Vitamin C

Answer: (C)

Pernicious anemia occurs when there is a deficiency of vitamin B-12 due to a lack of intrinsic factor, which is needed to absorb B-12 in the gut. Without enough B-12, red blood cell precursors can’t mature properly, leading to unusually large, abnormally shaped red blood cells (megaloblastic macrocytic anemia). B-12 also supports myelin in the nervous system, so deficiency can produce neurologic symptoms like numbness or balance problems. The lack of intrinsic factor is usually autoimmune, attacking the stomach’s parietal cells, so B-12 isn’t absorbed into the bloodstream even if the vitamin is present in the diet. Folate deficiency can cause a similar-looking anemia, but pernicious anemia specifically refers to B-12 deficiency from impaired absorption due to intrinsic factor loss. Other vitamins listed do not cause this condition.