Lipoproteins: Tangier disease: 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: Tangier disease

Sample item

A 14-year-old boy has enlarged, yellow-orange tonsils, mild hepatosplenomegaly and a peripheral neuropathy. Plasma HDL cholesterol is under 5 mg/dL, LDL cholesterol is low and triglycerides are mildly raised. Which defect is most likely?

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

The answer and the reasoning

C. ABCA1 transporter defect impairing efflux of cholesterol and phospholipid to apolipoprotein A-I

In Tangier disease, loss of ABCA1 prevents lipidation of nascent apoA-I, so HDL is cleared rapidly and cholesterol esters accumulate in macrophages, giving orange tonsils, hepatosplenomegaly and neuropathy. Plasma HDL is almost absent. The other options have different lipid profiles.

Option by option

  • A. CETP deficiency

    CETP deficiency raises HDL cholesterol and does not cause orange tonsils.

  • B. Lipoprotein lipase deficiency

    Lipoprotein lipase deficiency causes chylomicronaemia with eruptive xanthomas and pancreatitis.

  • C. ABCA1 transporter defect impairing efflux of cholesterol and phospholipid to apolipoprotein A-I (correct)

    Defective ABCA1-mediated efflux gives near-absent HDL with cholesteryl ester loading of macrophages.

  • D. Microsomal triglyceride transfer protein deficiency

    MTP deficiency causes abetalipoproteinaemia with absent apoB lipoproteins and fat malabsorption, not isolated 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, ABCA1 transporter defect impairing efflux of cholesterol and phospholipid to apolipoprotein A-I. In Tangier disease, loss of ABCA1 prevents lipidation of nascent apoA-I, so HDL is cleared rapidly and cholesterol esters accumulate in macrophages, giving orange tonsils, hepatosplenomegaly and neuropathy.

Why is "CETP deficiency" not the answer?

CETP deficiency raises HDL cholesterol and does not cause orange tonsils.

Why is "Lipoprotein lipase deficiency" not the answer?

Lipoprotein lipase deficiency causes chylomicronaemia with eruptive xanthomas and pancreatitis.

Why is "Microsomal triglyceride transfer protein deficiency" not the answer?

MTP deficiency causes abetalipoproteinaemia with absent apoB lipoproteins and fat malabsorption, not isolated low HDL.

What concept does this question test?

It tests Lipoproteins: Tangier disease in Biochemistry. Plasma HDL is almost absent. The other options have different lipid profiles.

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: Tangier disease?

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.