Immunology: Wiskott-Aldrich syndrome: 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: Wiskott-Aldrich syndrome

Sample item

A 1-year-old boy has eczema, recurrent ear infections and bleeding with petechiae. His platelet count is low and the platelets are small. Which statement about the underlying disease is correct?

AIt is X-linked, caused by mutation of the IL2RG geneBIt is autosomal recessive, caused by adenosine deaminase deficiencyCIt is X-linked, caused by mutation of the BTK geneDIt is X-linked, caused by mutation of the WAS gene affecting the actin cytoskeleton of haematopoietic cells

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

The answer and the reasoning

D. It is X-linked, caused by mutation of the WAS gene affecting the actin cytoskeleton of haematopoietic cells

Wiskott-Aldrich syndrome is an X-linked disorder of the WAS protein, which organises the actin cytoskeleton in blood cells. It gives the triad of eczema, microthrombocytopenia and recurrent infections, with a raised risk of autoimmunity and lymphoma. Stem cell transplantation is curative.

Option by option

A. It is X-linked, caused by mutation of the IL2RG gene
IL2RG mutation causes X-linked SCID with absent T cells, but not low platelets.
B. It is autosomal recessive, caused by adenosine deaminase deficiency
ADA deficiency causes autosomal recessive SCID without microthrombocytopenia.
C. It is X-linked, caused by mutation of the BTK gene
BTK mutation causes agammaglobulinaemia without eczema or thrombocytopenia.
D. It is X-linked, caused by mutation of the WAS gene affecting the actin cytoskeleton of haematopoietic cells (correct)
Correct. WAS gene mutation produces the eczema, small platelets and infection triad.

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.

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is D, It is X-linked, caused by mutation of the WAS gene affecting the actin cytoskeleton of haematopoietic cells. Wiskott-Aldrich syndrome is an X-linked disorder of the WAS protein, which organises the actin cytoskeleton in blood cells.

Why is "It is X-linked, caused by mutation of the IL2RG gene" not the answer?

IL2RG mutation causes X-linked SCID with absent T cells, but not low platelets.

Why is "It is autosomal recessive, caused by adenosine deaminase deficiency" not the answer?

ADA deficiency causes autosomal recessive SCID without microthrombocytopenia.

Why is "It is X-linked, caused by mutation of the BTK gene" not the answer?

BTK mutation causes agammaglobulinaemia without eczema or thrombocytopenia.

What concept does this question test?

It tests Immunology: Wiskott-Aldrich syndrome in Microbiology. It gives the triad of eczema, microthrombocytopenia and recurrent infections, with a raised risk of autoimmunity and lymphoma. Stem cell transplantation is curative.

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: Wiskott-Aldrich syndrome?

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.