Which statement describes Glanzmann thrombasthenia in platelet aggregation testing?

Which statement describes Glanzmann thrombasthenia in platelet aggregation testing?

• A. Markedly decreased aggregation to ADP
• B. Increased aggregation to ADP
• C. Normal aggregation to ADP
• D. Decreased aggregation to ristocetin

Answer: (A)

Glanzmann thrombasthenia shows a defect in platelet aggregation because there is a deficiency of the GPIIb/IIIa (integrin αIIbβ3) receptor on platelets. This receptor is essential for fibrinogen-mediated cross-linking of platelets to form aggregates. When an aggregating agent like ADP is used, platelets rely on GPIIb/IIIa to come together; without it, aggregation is markedly reduced. Ristocetin-induced aggregation, however, remains normal because that pathway depends on the interaction of von Willebrand factor with the GPIb-IX-V complex, which is intact in Glanzmann. So the hallmark is markedly decreased aggregation to ADP, while ristocetin-induced aggregation is normal.

Glanzmann thrombasthenia shows a defect in platelet aggregation because there is a deficiency of the GPIIb/IIIa (integrin αIIbβ3) receptor on platelets. This receptor is essential for fibrinogen-mediated cross-linking of platelets to form aggregates. When an aggregating agent like ADP is used, platelets rely on GPIIb/IIIa to come together; without it, aggregation is markedly reduced. Ristocetin-induced aggregation, however, remains normal because that pathway depends on the interaction of von Willebrand factor with the GPIb-IX-V complex, which is intact in Glanzmann. So the hallmark is markedly decreased aggregation to ADP, while ristocetin-induced aggregation is normal.