Immunology: anti-Smith antibody: practice question

A Microbiology 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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Microbiology · Immunology: anti-Smith antibody

Sample item

A 25-year-old woman has a malar rash, arthritis and proteinuria, and her antinuclear antibody test is strongly positive. Which of the following autoantibodies is highly specific for her probable diagnosis, even though it is present in only a minority of patients?

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

The answer and the reasoning

B. Anti-Smith antibody

Antibodies to the Smith antigen, a component of small nuclear ribonucleoprotein particles, are highly specific for systemic lupus erythematosus but are found in only about a quarter of patients. Antinuclear antibody is sensitive but not specific. Anti-histone antibodies characterise drug-induced lupus.

Option by option

  • A. Anti-histone antibody

    Anti-histone antibodies are typical of drug-induced lupus and are also found in idiopathic lupus, but they are not specific.

  • B. Anti-Smith antibody (correct)

    Correct. Anti-Sm is highly specific for lupus though insensitive.

  • C. Anti-centromere antibody

    Anti-centromere antibody is linked with limited cutaneous systemic sclerosis.

  • D. Anti-topoisomerase I antibody

    Anti-topoisomerase I (anti-Scl-70) is linked with diffuse systemic sclerosis.

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.

More Microbiology questions

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is B, Anti-Smith antibody. Antibodies to the Smith antigen, a component of small nuclear ribonucleoprotein particles, are highly specific for systemic lupus erythematosus but are found in only about a quarter of patients.

Why is "Anti-histone antibody" not the answer?

Anti-histone antibodies are typical of drug-induced lupus and are also found in idiopathic lupus, but they are not specific.

Why is "Anti-centromere antibody" not the answer?

Anti-centromere antibody is linked with limited cutaneous systemic sclerosis.

Why is "Anti-topoisomerase I antibody" not the answer?

Anti-topoisomerase I (anti-Scl-70) is linked with diffuse systemic sclerosis.

What concept does this question test?

It tests Immunology: anti-Smith antibody in Microbiology. Antinuclear antibody is sensitive but not specific. Anti-histone antibodies characterise drug-induced lupus.

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 Immunology: anti-Smith antibody?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology 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.