What is caused by a deficiency of Vitamin B12?

Appeared in: Haryana CHO - 2022

Explanation

Pernicious anemia is a specific type of megaloblastic anemia caused by the inability to absorb Vitamin B12.
This inability is due to a lack of Intrinsic Factor (IF), a protein made in the stomach that is necessary for B12 absorption in the ileum.
While dietary B12 deficiency can cause megaloblastic anemia, pernicious anemia specifically refers to the autoimmune condition that destroys IF-producing cells or IF itself.
The deficiency leads to both hematological issues (large, non-functional red blood cells) and neurological problems like paresthesia and gait issues.

Option A: Night-blindness (nyctalopia) is the classic sign of Vitamin A deficiency, not Vitamin B12 deficiency.
Option C: Rickets is a condition affecting bone development in children, characterized by soft and weak bones. It is caused by a deficiency of Vitamin D.
Option D: Scurvy is caused by a severe deficiency of Vitamin C (ascorbic acid). Its symptoms include bleeding gums, poor wound healing, and fatigue.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Vitamin Deficiencies and Associated Diseases as background academic context rather than a clinical decision trigger.
Understanding the cause of anemia is critical. Pernicious anemia requires lifelong B12 injections (cyanocobalamin or hydroxocobalamin) because the oral route is ineffective due to the lack of Intrinsic Factor.
Nurses must educate patients with pernicious anemia about the importance of adhering to their injection schedule to prevent irreversible neurological damage.
What if? If a patient with megaloblastic anemia is a strict vegan, the cause is more likely to be dietary B12 deficiency rather than pernicious anemia. This patient could potentially be treated with oral B12 supplements, unlike a patient with pernicious anemia.

How to Approach the Question

First, identify the core concept in the question stem: 'deficiency of Vitamin B12'.
This is a factual recall question. Access your knowledge about major vitamins and the diseases their deficiencies cause.
Evaluate each option: 'Night-blindness' is linked to Vitamin A. 'Rickets' is linked to Vitamin D. 'Scurvy' is linked to Vitamin C.
By elimination, 'Pernicious anemia' is the condition associated with Vitamin B12 deficiency.
Confirm the link: Vitamin B12 is essential for red blood cell formation, and its deficiency leads to a specific type of anemia called pernicious anemia.

Concept Tested & Keywords

Q5Zinr7FKVigRSFvX6c7HC

E6 Pharmacology Katzung 16e p. 934-936

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 2 — Subpart A (pp 1-239 of 478) p. 148-150

Practise the full Haryana CHO - 2022

Attempt every question from this paper in a timed mock, then review the full solution for each one.