Rheumatology: mechanism of mycophenolate: practice question

A General Medicine question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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General Medicine · Rheumatology: mechanism of mycophenolate

Sample item

A patient with class IV lupus nephritis is started on mycophenolate mofetil. Which enzyme does its active metabolite inhibit to limit lymphocyte proliferation?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. Inosine monophosphate dehydrogenase

Mycophenolic acid blocks inosine monophosphate dehydrogenase, depleting guanosine nucleotides. T and B lymphocytes depend on this de novo purine pathway, so they are selectively suppressed.

Option by option

  • A. Dihydroorotate dehydrogenase

    Dihydroorotate dehydrogenase is the target of leflunomide.

  • B. Calcineurin phosphatase

    Calcineurin is the target of tacrolimus and ciclosporin.

  • C. Dihydrofolate reductase

    Dihydrofolate reductase is the target of methotrexate.

  • D. Inosine monophosphate dehydrogenase (correct)

    Correct. Inhibition of this enzyme blocks de novo guanine nucleotide synthesis in lymphocytes.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this General Medicine question

What is the answer to this General Medicine question?

The best answer is D, Inosine monophosphate dehydrogenase. Mycophenolic acid blocks inosine monophosphate dehydrogenase, depleting guanosine nucleotides.

Why is "Dihydroorotate dehydrogenase" not the answer?

Dihydroorotate dehydrogenase is the target of leflunomide.

Why is "Calcineurin phosphatase" not the answer?

Calcineurin is the target of tacrolimus and ciclosporin.

Why is "Dihydrofolate reductase" not the answer?

Dihydrofolate reductase is the target of methotrexate.

What concept does this question test?

It tests Rheumatology: mechanism of mycophenolate in General Medicine. T and B lymphocytes depend on this de novo purine pathway, so they are selectively suppressed.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Rheumatology: mechanism of mycophenolate?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General Medicine questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.