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 28-year-old man is brought after prolonged immobilisation following a drug overdose. His urine is dark brown, the dipstick is strongly positive for blood, and microscopy shows no red cells. Serum creatinine is rising and potassium is high. Which laboratory finding best supports the diagnosis?

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

The answer and the reasoning

C. Markedly raised serum creatine kinase, mostly the MM isoenzyme

Rhabdomyolysis releases myoglobin and muscle enzymes, so total CK, mostly CK-MM, is raised, often more than five times normal. Myoglobin passes into urine, where it reacts with the dipstick haem pad without red cells and, with volume depletion, injures tubules, causing acute kidney injury and hyperkalaemia. Early aggressive intravenous fluids prevent renal failure.

Option by option

  • A. Raised alkaline phosphatase of bone origin

    Bone ALP reflects osteoblast activity and not muscle breakdown.

  • B. Raised serum lipase

    Lipase rises in pancreatitis and does not explain pigmenturia.

  • C. Markedly raised serum creatine kinase, mostly the MM isoenzyme (correct)

    Correct. A high CK of the MM type with pigment-positive urine and no red cells points to rhabdomyolysis.

  • D. Markedly raised serum CK-MB with a normal total CK

    Isolated CK-MB elevation suggests myocardial injury and is not the muscle pattern.

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 C, Markedly raised serum creatine kinase, mostly the MM isoenzyme. Rhabdomyolysis releases myoglobin and muscle enzymes, so total CK, mostly CK-MM, is raised, often more than five times normal.

Why is "Raised alkaline phosphatase of bone origin" not the answer?

Bone ALP reflects osteoblast activity and not muscle breakdown.

Why is "Raised serum lipase" not the answer?

Lipase rises in pancreatitis and does not explain pigmenturia.

Why is "Markedly raised serum CK-MB with a normal total CK" not the answer?

Isolated CK-MB elevation suggests myocardial injury and is not the muscle pattern.

What concept does this question test?

It tests Clinical biochemistry: rhabdomyolysis in Biochemistry. Myoglobin passes into urine, where it reacts with the dipstick haem pad without red cells and, with volume depletion, injures tubules, causing acute kidney injury and hyperkalaemia. Early aggressive intravenous fluids prevent renal failure.

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.