Question

A 30-year-old woman presents with easy fatigability, exertional dyspnea and weight loss. She also reports frequent falls. On examination there is a bilateral decrease in vibration sense. Her hemoglobin is 8.2 g%. She was treated with folate; her anemia improved but her neurological symptoms worsened. What is the most probable reason for her condition?

• A. Folate was not absorbed
• B. Unmasked pyridoxine deficiency
• C. Deficiency of folate reductase in the CNS
• D. Folate therapy caused rapid use of vitamin B12 stores, aggravating symptoms

Hint:

Anemia improves but the cord signs worsen, what happens to B12 stores when you push folate alone?

Answer 1

The Correct Option is D

Step 1: The picture, anemia plus a symmetric loss of vibration sense and frequent falls, points to vitamin B12 deficiency with subacute combined degeneration of the cord, not pure folate deficiency.
Step 2: Vitamin B12 is needed to regenerate tetrahydrofolate, the active folate form used for DNA synthesis. Giving folate alone can correct the megaloblastic anemia because it bypasses this block.
Step 3: But folate does nothing for the neurologic disease. Worse, the surge of DNA synthesis after folate consumes the remaining B12, deepening the deficiency and worsening the neuropathy.
This is why B12 deficiency must be excluded before treating megaloblastic anemia with folate. The answer is option 4.
Ref: Standard hematology and biochemistry texts.