Nephrology: post-streptococcal glomerulonephritis: 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 · Nephrology: post-streptococcal glomerulonephritis

Sample item

An 8-year-old boy has cola-coloured urine, periorbital puffiness and blood pressure of 140/90 mmHg two weeks after a skin infection. Which serological pattern would you expect, and what is the expected course?

ALow C3 with normal C4, remaining low beyond 3 monthsBNormal C3 and C4 throughout the illnessCLow C3 and low C4, normalising within one weekDLow C3 with normal C4, returning to normal within 6 to 8 weeks

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

The answer and the reasoning

D. Low C3 with normal C4, returning to normal within 6 to 8 weeks

Post-streptococcal glomerulonephritis activates the alternative complement pathway, so C3 is low with normal C4. Complement levels recover within 6 to 8 weeks, and persistent hypocomplementaemia beyond 8 to 12 weeks should prompt consideration of C3 glomerulopathy or membranoproliferative disease. Management is supportive, with antibiotics for residual infection, diuretics and antihypertensives.

Option by option

A. Low C3 with normal C4, remaining low beyond 3 months
Persistently low C3 beyond 3 months suggests C3 glomerulopathy or MPGN, not simple post-infectious disease.
B. Normal C3 and C4 throughout the illness
A normal C3 would be typical of IgA nephropathy, not post-infectious disease.
C. Low C3 and low C4, normalising within one week
Low C3 with low C4 suggests classical pathway activation as in lupus nephritis, not this illness.
D. Low C3 with normal C4, returning to normal within 6 to 8 weeks (correct)
Correct. Alternative pathway activation lowers C3 only, and it normalises within about 6 to 8 weeks.

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.

Questions about this General Medicine question

What is the answer to this General Medicine question?

The best answer is D, Low C3 with normal C4, returning to normal within 6 to 8 weeks. Post-streptococcal glomerulonephritis activates the alternative complement pathway, so C3 is low with normal C4.

Why is "Low C3 with normal C4, remaining low beyond 3 months" not the answer?

Persistently low C3 beyond 3 months suggests C3 glomerulopathy or MPGN, not simple post-infectious disease.

Why is "Normal C3 and C4 throughout the illness" not the answer?

A normal C3 would be typical of IgA nephropathy, not post-infectious disease.

Why is "Low C3 and low C4, normalising within one week" not the answer?

Low C3 with low C4 suggests classical pathway activation as in lupus nephritis, not this illness.

What concept does this question test?

It tests Nephrology: post-streptococcal glomerulonephritis in General Medicine. Complement levels recover within 6 to 8 weeks, and persistent hypocomplementaemia beyond 8 to 12 weeks should prompt consideration of C3 glomerulopathy or membranoproliferative disease. Management is supportive, with antibiotics for residual infection, diuretics and antihypertensives.

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 Nephrology: post-streptococcal glomerulonephritis?

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.