Bernard-Soulier syndrome has a characteristic finding related to platelets. Which statement best describes this?

• A. Platelets are abnormally small
• B. Platelets show increased ristocetin-induced aggregation
• C. Platelets are abnormally large (macrothrombocytes)
• D. Platelets clump excessively on smear

Answer: (C)

Bernard-Soulier syndrome centers on a defect in the platelet GPIb-IX-V receptor, which is needed for platelets to bind von Willebrand factor and adhere to the damaged vessel wall. Because this adhesion step is impaired, the platelets often appear abnormal on the smear, most notably as platelets that are abnormally large—macrothrombocytes. This giant-platelet finding is the hallmark feature and is why the description of abnormally large platelets is the best choice.

In this condition, ristocetin-induced platelet aggregation is not increased; it is reduced or absent due to the defective GPIb-vWF interaction. Platelets clumping on smear isn’t a defining characteristic of Bernard-Soulier.