Clinical biochemistry: rhabdomyolysis: practice question

A Biochemistry 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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Biochemistry · Clinical biochemistry: rhabdomyolysis

Sample item

A 24-year-old recruit collapses after a long forced march and passes tea-coloured urine. Urine dipstick is strongly positive for blood, but microscopy shows no red cells. Serum CK is 40,000 U/L. Which pigment is responsible?

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

The answer and the reasoning

B. Myoglobin

Rhabdomyolysis releases myoglobin and CK from damaged muscle. Myoglobin is filtered and has peroxidase-like activity, so the dipstick reads positive for blood though no red cells are seen. It precipitates in tubules and causes acute kidney injury, so aggressive intravenous fluids are started and potassium is watched.

Option by option

  • A. Haemosiderin

    Haemosiderin appears in urine days after intravascular haemolysis and is detected by Prussian blue staining.

  • B. Myoglobin (correct)

    Correct. Myoglobinuria gives a positive dipstick for blood without red cells.

  • C. Porphobilinogen

    Porphobilinogen causes urine to darken on standing in acute porphyria, with no raised CK.

  • D. Bilirubin

    Bilirubin colours urine dark yellow-brown and does not make the dipstick positive for blood.

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 Biochemistry question

What is the answer to this Biochemistry question?

The best answer is B, Myoglobin. Rhabdomyolysis releases myoglobin and CK from damaged muscle.

Why is "Haemosiderin" not the answer?

Haemosiderin appears in urine days after intravascular haemolysis and is detected by Prussian blue staining.

Why is "Porphobilinogen" not the answer?

Porphobilinogen causes urine to darken on standing in acute porphyria, with no raised CK.

Why is "Bilirubin" not the answer?

Bilirubin colours urine dark yellow-brown and does not make the dipstick positive for blood.

What concept does this question test?

It tests Clinical biochemistry: rhabdomyolysis in Biochemistry. Myoglobin is filtered and has peroxidase-like activity, so the dipstick reads positive for blood though no red cells are seen. It precipitates in tubules and causes acute kidney injury, so aggressive intravenous fluids are started and potassium is watched.

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 Clinical biochemistry: rhabdomyolysis?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry 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.