Pernicious anemia is caused by the deficiency of which Vitamin?

NIA - 29 January 2023

Applied Nutrition & Dietetics

Easy

Appeared in: NIA - 29 January 2023

Explanation

Pernicious anemia is a type of megaloblastic anemia specifically caused by a deficiency in Vitamin B₁₂.
The core issue in pernicious anemia is an autoimmune gastritis that leads to the loss of gastric parietal cells.
These parietal cells produce intrinsic factor, a protein essential for the absorption of Vitamin B₁₂ in the terminal ileum.
Without intrinsic factor, Vitamin B₁₂ cannot be absorbed, leading to deficiency and subsequent anemia and neurological symptoms.
This is distinct from dietary Vitamin B₁₂ deficiency, as the problem lies in absorption, not intake.

Option A: Vitamin A deficiency does not cause pernicious anemia. Its deficiency primarily affects vision and epithelial cell integrity.
Option B: Vitamin D deficiency is related to bone health and calcium metabolism, not pernicious anemia.
Option D: The term 'Vitamin B' is too general. While pernicious anemia is caused by a B vitamin (B₁₂), this option is not specific enough. Other B vitamins cause different conditions (e.g., Vitamin B₁ deficiency causes beriberi).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain The specific vitamin deficiency that causes pernicious anemia as background academic context rather than a clinical decision trigger.
It is crucial for nurses to understand that pernicious anemia is an absorption problem, not a dietary one. Treatment requires bypassing the gut, typically with intramuscular B₁₂ injections or very high-dose oral supplements.
Nurses must monitor for both hematologic (fatigue, pallor) and neurologic (paresthesia, ataxia, confusion) signs of B₁₂ deficiency, as neurological damage can be irreversible if not treated promptly.
What if? If a patient with megaloblastic anemia is treated only with folic acid, their anemia might improve, but the underlying B₁₂ deficiency will persist. This can mask the diagnosis and allow severe, irreversible neurological damage to progress.

How to Approach the Question

First, identify the key term in the question: 'Pernicious anemia'.
This is a factual recall question. Access your knowledge about the specific cause of this named condition.
Recall that 'pernicious' refers to the insidious and harmful nature of the disease, which stems from an inability to absorb a specific nutrient.
Evaluate the options. Associate Vitamin B₁₂ with its role in red blood cell formation and neurological function, and its specific absorption mechanism involving intrinsic factor.
Eliminate the other vitamins by recalling the classic diseases associated with their deficiencies (Vitamin A with eye issues, Vitamin D with bone issues).

Concept Tested & Keywords

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E6 Pathology- ROBBINS & COTRAN PATHOLOGIC BASIS OF DISEASE 10TH Ed p. 655-657

E6 Medicine Harrison 22e Part 2 p. 510-512