Blood and immunity: hereditary angioedema: practice question

A Physiology 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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Physiology · Blood and immunity: hereditary angioedema

Sample item

A 22-year-old has recurrent non-itchy swelling of the face, bowel wall colic and laryngeal swelling after dental work. There is no urticaria, antihistamines and adrenaline give little relief, and C4 is low. Which mediator causes the swelling?

ABradykininBHistamineCPlatelet-activating factorDLeukotriene C4

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

The answer and the reasoning

A. Bradykinin

Hereditary angioedema results from C1 inhibitor deficiency. Unchecked activation of kallikrein and factor XII generates bradykinin, which increases vascular permeability. Histamine-targeted treatments therefore fail, and C4 is low because uninhibited C1 consumes it.

Option by option

A. Bradykinin (correct)
Correct. Bradykinin from unchecked kallikrein activity causes the swelling.
B. Histamine
Histamine causes itchy urticarial swelling that responds to antihistamines.
C. Platelet-activating factor
PAF contributes to allergic reactions rather than to C1 inhibitor deficiency.
D. Leukotriene C4
Leukotriene C4 is a mast cell mediator of bronchoconstriction and permeability in allergy.

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 Physiology question

What is the answer to this Physiology question?

The best answer is A, Bradykinin. Hereditary angioedema results from C1 inhibitor deficiency.

Why is "Histamine" not the answer?

Histamine causes itchy urticarial swelling that responds to antihistamines.

Why is "Platelet-activating factor" not the answer?

PAF contributes to allergic reactions rather than to C1 inhibitor deficiency.

Why is "Leukotriene C4" not the answer?

Leukotriene C4 is a mast cell mediator of bronchoconstriction and permeability in allergy.

What concept does this question test?

It tests Blood and immunity: hereditary angioedema in Physiology. Unchecked activation of kallikrein and factor XII generates bradykinin, which increases vascular permeability. Histamine-targeted treatments therefore fail, and C4 is low because uninhibited C1 consumes it.

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 Blood and immunity: hereditary angioedema?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology 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.