Renal: membranoproliferative glomerulonephritis: practice question

A Pathology 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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Pathology · Renal: membranoproliferative glomerulonephritis

Sample item

A 14-year-old girl has haematuria, proteinuria and persistently low serum C3 with normal C4. Light microscopy shows lobulated glomeruli with a tram-track basement membrane, and electron microscopy shows ribbon-like intramembranous dense deposits. What is responsible for the low complement?

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

The answer and the reasoning

A. C3 nephritic factor, an autoantibody that stabilises alternative pathway C3 convertase

Dense deposit disease (MPGN type II, now C3 glomerulopathy) is due to uncontrolled alternative pathway activation, often because of C3 nephritic factor. This causes persistent hypocomplementaemia with a normal C4. Cryoglobulinaemic MPGN lowers C4 through classical pathway activation.

Option by option

  • A. C3 nephritic factor, an autoantibody that stabilises alternative pathway C3 convertase (correct)

    Correct. C3 nephritic factor stabilises C3 convertase and consumes C3.

  • B. Cryoglobulins with hepatitis C

    Cryoglobulins activate the classical pathway, so C4 would also be low.

  • C. Streptococcal antigen planted in the subepithelium

    Streptococcal antigens cause subepithelial humps with transient low C3 rather than persistent intramembranous deposits.

  • D. Anti-glomerular basement membrane antibody

    Anti-GBM antibodies produce linear IgG deposition and crescentic disease with normal complement.

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 Pathology question

What is the answer to this Pathology question?

The best answer is A, C3 nephritic factor, an autoantibody that stabilises alternative pathway C3 convertase. Dense deposit disease (MPGN type II, now C3 glomerulopathy) is due to uncontrolled alternative pathway activation, often because of C3 nephritic factor.

Why is "Cryoglobulins with hepatitis C" not the answer?

Cryoglobulins activate the classical pathway, so C4 would also be low.

Why is "Streptococcal antigen planted in the subepithelium" not the answer?

Streptococcal antigens cause subepithelial humps with transient low C3 rather than persistent intramembranous deposits.

Why is "Anti-glomerular basement membrane antibody" not the answer?

Anti-GBM antibodies produce linear IgG deposition and crescentic disease with normal complement.

What concept does this question test?

It tests Renal: membranoproliferative glomerulonephritis in Pathology. This causes persistent hypocomplementaemia with a normal C4. Cryoglobulinaemic MPGN lowers C4 through classical pathway activation.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Renal: membranoproliferative glomerulonephritis?

Learn each disease as a bundle: cause, key histology, markers, and the clinical hallmark. Then use the flashcards and the other Pathology 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.