Bernard-Soulier syndrome is due to deficiency of which complex, leading to poor adhesion of von Willebrand factor and thrombocytopenia with large platelets?

Get ready for the CAMLPR Hematology Test. Use our quizzes, flashcards, and detailed explanations to enhance your understanding. Prepare confidently for your exam!

Multiple Choice

Bernard-Soulier syndrome is due to deficiency of which complex, leading to poor adhesion of von Willebrand factor and thrombocytopenia with large platelets?

The key idea is that platelet adhesion to damaged vessels starts when the von Willebrand factor binds to the GPIb-IX-V complex on the platelet surface. In Bernard-Soulier syndrome this complex is deficient, so platelets cannot effectively adhere to exposed von Willebrand factor, especially under high shear, leading to defective primary hemostasis. The result is bleeding tendencies, thrombocytopenia, and notably large platelets (macrothrombocytes). Other glycoprotein complexes serve different roles: GPIIb-IIIa is the fibrinogen receptor required for platelet-platelet aggregation, so its defect causes Glanzmann thrombasthenia; GPIa-IIa is a collagen receptor involved in adhesion to collagen. Thus, the deficiency described here points to the GPIb-IX-V complex as the cause.

The key idea is that platelet adhesion to damaged vessels starts when the von Willebrand factor binds to the GPIb-IX-V complex on the platelet surface. In Bernard-Soulier syndrome this complex is deficient, so platelets cannot effectively adhere to exposed von Willebrand factor, especially under high shear, leading to defective primary hemostasis. The result is bleeding tendencies, thrombocytopenia, and notably large platelets (macrothrombocytes).

Other glycoprotein complexes serve different roles: GPIIb-IIIa is the fibrinogen receptor required for platelet-platelet aggregation, so its defect causes Glanzmann thrombasthenia; GPIa-IIa is a collagen receptor involved in adhesion to collagen. Thus, the deficiency described here points to the GPIb-IX-V complex as the cause.

More practice questions