Lipoproteins: dyslipidaemia: 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 · Lipoproteins: dyslipidaemia

Sample item

A child has recurrent abdominal pain, eruptive xanthomas and lipaemia retinalis. The plasma is creamy, with a milky layer on standing at 4 degrees and a clear infranatant. Which enzyme is likely deficient?

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

The answer and the reasoning

C. Lipoprotein lipase (or its cofactor apo C-II)

Lipoprotein lipase deficiency (familial chylomicronaemia, type I) prevents clearance of chylomicrons, which float as a cream layer. Triglycerides are very high, causing pancreatitis, eruptive xanthomas and lipaemia retinalis. Cholesterol is only mildly raised.

Option by option

  • A. LDL receptor

    LDL receptor deficiency causes familial hypercholesterolaemia with tendon xanthomas.

  • B. Apolipoprotein B-100 binding domain

    Apo B-100 defects also raise LDL, not chylomicrons.

  • C. Lipoprotein lipase (or its cofactor apo C-II) (correct)

    Correct. Chylomicrons cannot be hydrolysed.

  • D. LCAT

    LCAT deficiency causes corneal opacities and anaemia with low HDL.

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, Lipoprotein lipase (or its cofactor apo C-II). Lipoprotein lipase deficiency (familial chylomicronaemia, type I) prevents clearance of chylomicrons, which float as a cream layer.

Why is "LDL receptor" not the answer?

LDL receptor deficiency causes familial hypercholesterolaemia with tendon xanthomas.

Why is "Apolipoprotein B-100 binding domain" not the answer?

Apo B-100 defects also raise LDL, not chylomicrons.

Why is "LCAT" not the answer?

LCAT deficiency causes corneal opacities and anaemia with low HDL.

What concept does this question test?

It tests Lipoproteins: dyslipidaemia in Biochemistry. Triglycerides are very high, causing pancreatitis, eruptive xanthomas and lipaemia retinalis. Cholesterol is only mildly raised.

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 Lipoproteins: dyslipidaemia?

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.