A 5-year-old boy has prolonged bleeding time, normal platelet count, and absent platelet aggregation to ALL agonists (ADP, collagen, thrombin) except ristocetin. This is diagnostic of:

• A Bernard-Soulier syndrome (GPIb-IX-V deficiency)
• B von Willebrand disease type 1
• C Glanzmann thrombasthenia (GPIIb/IIIa deficiency) ✓
• D Delta granule storage pool disorder

Explanation

Glanzmann thrombasthenia results from absent or dysfunctional GPIIb/IIIa (integrin alphaIIbbeta3), the fibrinogen receptor required for platelet aggregation. Platelets adhere normally (GPIb intact) but cannot aggregate — aggregation to ALL agonists is absent, while ristocetin-induced vWF-mediated platelet agglutination is preserved. Bernard-Soulier syndrome has absent ristocetin agglutination (GPIb defect) but normal aggregation to other agonists.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.