Megaloblastic anemia is caused by deficiency of:

RUHS, Jaipur, PB B.Sc Nursing Entrance-2020

Applied Nutrition & Dietetics

Easy

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2020

Explanation

Megaloblastic anemia results from impaired DNA synthesis, which affects rapidly dividing cells like hematopoietic precursors in the bone marrow.
Vitamin B12 (Cobalamin) is a crucial co-factor in the metabolic pathways required for DNA synthesis, specifically in the conversion of homocysteine to methionine, which is linked to folate metabolism.
A deficiency in Vitamin B12 leads to the trapping of folate in an unusable form (the 'methyl-folate trap'), which halts DNA production and causes nuclear-cytoplasmic asynchrony in developing red blood cells.
This process results in the formation of large, immature, and dysfunctional red blood cells (megaloblasts), which are the hallmark of this type of anemia.

Option A: Vitamin B1 (Thiamine) deficiency does not cause megaloblastic anemia. It primarily affects the nervous and cardiovascular systems.
Option B: Vitamin B2 (Riboflavin) deficiency is associated with ariboflavinosis, which presents with symptoms like cheilosis and glossitis, but it does not cause megaloblastic anemia.
Option C: Vitamin B6 (Pyridoxine) deficiency is linked to sideroblastic anemia (a type of microcytic anemia where iron is not properly incorporated into hemoglobin) and peripheral neuropathy, not megaloblastic anemia.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Causes of Megaloblastic Anemia as background academic context rather than a clinical decision trigger.
Nurses must be able to differentiate between folate and Vitamin B12 deficiency anemia, as the treatment differs and misdiagnosis can have serious consequences. Specifically, treating a B12 deficient patient with only folic acid can correct the anemia but will allow the irreversible neurological damage to progress.
Key nursing interventions include dietary counseling for at-risk populations (e.g., vegans, elderly, patients post-gastrectomy), administering B12 injections for pernicious anemia, and monitoring for neurological symptoms like paresthesia, ataxia, and memory changes.
What if? If a patient with megaloblastic anemia also presents with numbness and tingling in their hands and feet, the nurse should have a high suspicion of Vitamin B12 deficiency specifically, as these neurological symptoms are not associated with folate deficiency. This requires urgent reporting and management to prevent permanent nerve damage.

How to Approach the Question

First, identify the core concept in the question stem: 'Megaloblastic anemia'.
Next, recall the primary causes of this specific type of anemia. The key is that it's a macrocytic anemia caused by impaired DNA synthesis.
Remember that the two most common causes are Vitamin B12 deficiency and Folic Acid (Vitamin B9) deficiency.
Scan the options provided: Vitamin B1, Vitamin B2, Vitamin B6, and Vitamin B12.
Select the option that matches one of the known primary causes. In this case, Vitamin B12 is listed.
Mentally rule out the other options by recalling the distinct conditions associated with their deficiencies (e.g., B1 -> Beriberi, B6 -> Sideroblastic anemia).

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