Blood and immunity: platelet adhesion: 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: platelet adhesion

Sample item

An infant has thrombocytopenia with giant platelets and mucosal bleeding. Ristocetin does not agglutinate the platelets, and adding normal plasma does not correct this. Which defect fits best?

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

The answer and the reasoning

B. Absent platelet glycoprotein Ib-IX-V receptor

Adhesion to subendothelium needs platelet GPIb to bind von Willebrand factor. When the receptor is missing, as in Bernard-Soulier syndrome, ristocetin agglutination fails and normal plasma cannot correct it because vWF itself is normal. Giant platelets and low counts are typical.

Option by option

  • A. Absent glycoprotein IIb/IIIa

    Absent GPIIb/IIIa gives normal ristocetin agglutination and normal platelet size.

  • B. Absent platelet glycoprotein Ib-IX-V receptor (correct)

    Correct. The platelet receptor for vWF is missing, so adding normal plasma does not help.

  • C. Deficient factor VIII

    Factor VIII deficiency prolongs the aPTT but does not impair ristocetin agglutination.

  • D. Deficient plasma von Willebrand factor

    Plasma vWF deficiency would be corrected by adding normal plasma and platelets would be of normal size.

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 Physiology question

What is the answer to this Physiology question?

The best answer is B, Absent platelet glycoprotein Ib-IX-V receptor. Adhesion to subendothelium needs platelet GPIb to bind von Willebrand factor.

Why is "Absent glycoprotein IIb/IIIa" not the answer?

Absent GPIIb/IIIa gives normal ristocetin agglutination and normal platelet size.

Why is "Deficient factor VIII" not the answer?

Factor VIII deficiency prolongs the aPTT but does not impair ristocetin agglutination.

Why is "Deficient plasma von Willebrand factor" not the answer?

Plasma vWF deficiency would be corrected by adding normal plasma and platelets would be of normal size.

What concept does this question test?

It tests Blood and immunity: platelet adhesion in Physiology. When the receptor is missing, as in Bernard-Soulier syndrome, ristocetin agglutination fails and normal plasma cannot correct it because vWF itself is normal. Giant platelets and low counts are typical.

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: platelet adhesion?

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.