Immunodeficiency: common variable immunodeficiency: practice question

A Pathology 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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Pathology · Immunodeficiency: common variable immunodeficiency

Sample item

A 28-year-old man has had recurrent sinusitis and pneumonia since adolescence, chronic Giardia diarrhoea and nodular lymphoid hyperplasia of the gut. All immunoglobulin classes are low and vaccine responses are poor. Which feature distinguishes his condition from X-linked agammaglobulinaemia?

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

The answer and the reasoning

C. Normal or near-normal numbers of circulating B cells that fail to differentiate into plasma cells

Common variable immunodeficiency is a heterogeneous disorder presenting in the second to fourth decade with hypogammaglobulinaemia and recurrent sinopulmonary and gut infections. B cells are present in normal or near-normal numbers but do not mature into antibody-secreting plasma cells. Autoimmune disease, granulomas and lymphoma are associated.

Option by option

  • A. Raised serum IgM with absent IgG due to a CD40 ligand defect

    Raised IgM with low IgG is hyper-IgM syndrome from a CD40 ligand defect, which presents in early childhood.

  • B. Hypoplastic thymus with a low T-cell count

    A hypoplastic thymus is DiGeorge syndrome, a T-cell disorder.

  • C. Normal or near-normal numbers of circulating B cells that fail to differentiate into plasma cells (correct)

    Correct. B cells are present, which separates it from X-linked agammaglobulinaemia with absent B cells.

  • D. Absent circulating B cells due to a mutation in Bruton tyrosine kinase

    Absent B cells with a BTK mutation describes X-linked agammaglobulinaemia, which presents in infant boys.

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 Pathology question

What is the answer to this Pathology question?

The best answer is C, Normal or near-normal numbers of circulating B cells that fail to differentiate into plasma cells. Common variable immunodeficiency is a heterogeneous disorder presenting in the second to fourth decade with hypogammaglobulinaemia and recurrent sinopulmonary and gut infections.

Why is "Raised serum IgM with absent IgG due to a CD40 ligand defect" not the answer?

Raised IgM with low IgG is hyper-IgM syndrome from a CD40 ligand defect, which presents in early childhood.

Why is "Hypoplastic thymus with a low T-cell count" not the answer?

A hypoplastic thymus is DiGeorge syndrome, a T-cell disorder.

Why is "Absent circulating B cells due to a mutation in Bruton tyrosine kinase" not the answer?

Absent B cells with a BTK mutation describes X-linked agammaglobulinaemia, which presents in infant boys.

What concept does this question test?

It tests Immunodeficiency: common variable immunodeficiency in Pathology. B cells are present in normal or near-normal numbers but do not mature into antibody-secreting plasma cells. Autoimmune disease, granulomas and lymphoma are associated.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Immunodeficiency: common variable immunodeficiency?

Learn each disease as a bundle: cause, key histology, markers, and the clinical hallmark. Then use the flashcards and the other Pathology 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.