Genetic and metabolic disorders: X-linked agammaglobulinaemia: practice question

A Pediatrics 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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Pediatrics · Genetic and metabolic disorders: X-linked agammaglobulinaemia

Sample item

A 10-month-old boy has had repeated pneumococcal pneumonia and sinusitis since 6 months of age. Tonsils are absent and lymph nodes are not palpable. Which finding is expected?

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

The answer and the reasoning

A. Very low immunoglobulins of all classes and absent CD19 B cells

X-linked agammaglobulinaemia (Bruton) is caused by BTK mutation, which blocks B-cell maturation. Recurrent infections with encapsulated bacteria begin after maternal IgG wanes at about 6 months. Treatment is regular immunoglobulin replacement.

Option by option

  • A. Very low immunoglobulins of all classes and absent CD19 B cells (correct)

    Correct. Absent B cells and low immunoglobulins after 6 months explain the picture.

  • B. Elevated IgE and eosinophilia

    High IgE and eosinophilia occur in hyper-IgE syndrome with staphylococcal abscesses.

  • C. Absent T cells with normal immunoglobulins

    Absent T cells are seen in severe combined immunodeficiency, with infections from the first weeks.

  • D. Neutrophils failing to produce superoxide

    A failure of superoxide production is chronic granulomatous disease.

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 Pediatrics question

What is the answer to this Pediatrics question?

The best answer is A, Very low immunoglobulins of all classes and absent CD19 B cells. X-linked agammaglobulinaemia (Bruton) is caused by BTK mutation, which blocks B-cell maturation.

Why is "Elevated IgE and eosinophilia" not the answer?

High IgE and eosinophilia occur in hyper-IgE syndrome with staphylococcal abscesses.

Why is "Absent T cells with normal immunoglobulins" not the answer?

Absent T cells are seen in severe combined immunodeficiency, with infections from the first weeks.

Why is "Neutrophils failing to produce superoxide" not the answer?

A failure of superoxide production is chronic granulomatous disease.

What concept does this question test?

It tests Genetic and metabolic disorders: X-linked agammaglobulinaemia in Pediatrics. Recurrent infections with encapsulated bacteria begin after maternal IgG wanes at about 6 months. Treatment is regular immunoglobulin replacement.

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 Genetic and metabolic disorders: X-linked agammaglobulinaemia?

Memorise milestones and the vaccine schedule as tables and revise them often. Then use the flashcards and the other Pediatrics 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.