Pernicious anemia is caused by the deficiency of which vitamin?

Bihar CHO - 2021

Applied Nutrition & Dietetics

Easy

Appeared in: Bihar CHO - 2021

Explanation

Pernicious anemia is a type of megaloblastic anemia resulting from Vitamin B12 deficiency.
The core cause is an autoimmune gastritis that leads to a lack of intrinsic factor, a protein secreted by stomach parietal cells that is necessary for Vitamin B12 absorption in the ileum.
This deficiency uniquely causes both hematologic changes (large, immature red blood cells) and progressive, potentially irreversible neurological damage.
Key diagnostic markers include low serum B12, elevated methylmalonic acid and homocysteine levels, and the presence of antibodies against intrinsic factor.

Option A: Vitamin B6 (pyridoxine) deficiency does not cause pernicious anemia. It is associated with sideroblastic anemia, characterized by small, pale red blood cells (microcytic anemia), and can also cause skin and nerve problems.
Option C: Vitamin B9 (folate) deficiency causes megaloblastic anemia, which is hematologically similar to B12 deficiency. However, it does not cause the neurological symptoms characteristic of pernicious anemia. Treating a B12 deficiency with folate can mask the anemia while allowing neurological damage to progress.
Option D: Vitamin A deficiency is unrelated to pernicious anemia. Its deficiency primarily affects vision (causing night blindness), immune function, and skin integrity (xerophthalmia).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Etiology of Pernicious Anemia as background academic context rather than a clinical decision trigger.
Nurses must recognize that pernicious anemia requires lifelong treatment, typically with intramuscular B12 injections, because the underlying absorption defect is permanent.
A key nursing assessment is to monitor for neurological symptoms like paresthesia, ataxia, and cognitive changes, as these indicate B12 deficiency and require prompt intervention to prevent irreversible damage.
Patient education is critical. The nurse must explain that while folic acid is important, taking it alone can mask a B12 deficiency, allowing neurological disease to worsen. The patient must understand the importance of continued B12 therapy.

How to Approach the Question

First, identify the key term in the question: 'Pernicious anemia'. This is a specific medical diagnosis.
Recall the definition and pathophysiology of pernicious anemia. The term 'pernicious' itself hints at a serious, insidious condition. The core defect is not dietary lack but a failure of absorption.
Connect the absorption failure to its cause: lack of 'intrinsic factor'.
Link intrinsic factor to the specific vitamin it helps absorb: Vitamin B12.
Evaluate the options. Differentiate B12 deficiency from other B-vitamin deficiencies. Remember that B9 (folate) also causes megaloblastic anemia but lacks the neurological component, making it a key distractor. B6 and A cause entirely different types of anemia or other conditions.
Select the option that correctly links pernicious anemia to Vitamin B12 deficiency.

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