Question
A patient with megaloblastic anemia is mistakenly treated with folate alone, after which the neurological symptoms worsen rather than improve. Which of the following best explains this phenomenon?
| A. |
Folate trap
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| B. |
Homocysteine accumulation
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| C. |
Masking of vitamin B12 deficiency by folate therapy
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| D. |
Pernicious anemia due to intrinsic factor deficiency
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Show Answer
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Correct Answer � A
Explanation
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Folate trap hypothesis explains that in vitamin B12 deficiency, folate gets trapped as methyl tetrahydrofolate (N5-methyl THF).
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B12 is essential for the conversion of N5-methyl THF to THF via methionine synthase, which also converts homocysteine to methionine.
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Without B12, THF cannot be regenerated, impairing DNA synthesis and leading to megaloblastic anemia.
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Giving folate alone may improve anemia but does not correct the neurological deficits, which continue to worsen due to methylmalonic acid accumulation in B12 deficiency.
Reasons to rule out other options:
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B. Homocysteine accumulation: It occurs, but it’s not the mechanism causing neurological worsening.
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C. Masking of vitamin B12 deficiency: It’s a clinical concern but doesn’t mechanistically explain worsening neuro symptoms like the folate trap does.
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D. Pernicious anemia: It’s a cause of B12 deficiency, not an explanation for symptom worsening after folate therapy.
