A 25-year-old woman has recurrent mucocutaneous bleeding. Platelet count is normal. Bleeding time is prolonged. PT and aPTT are normal. Platelet aggregation studies show normal aggregation with ADP and collagen but absent aggregation with ristocetin. Von Willebrand factor antigen level is normal. What is the diagnosis?

• A Bernard-Soulier syndrome — deficiency of GPIb-IX-V complex, giant platelets on smear ✓
• B Glanzmann thrombasthenia — deficiency of GPIIb/IIIa (αIIbβ3), normal platelet size
• C Von Willebrand disease type 2B — gain-of-function VWF mutation with increased ristocetin cofactor activity
• D Platelet-type (pseudo) VWD — gain-of-function GPIb mutation mimicking vWD type 2B

Explanation

The key finding is absent ristocetin-induced platelet agglutination with normal VWF — ristocetin requires both vWF and the GPIb receptor on platelets to work. In Bernard-Soulier syndrome, GPIb-IX-V is absent/deficient, so ristocetin cannot agglutinate platelets even with normal VWF. Glanzmann thrombasthenia shows absent aggregation with ADP, collagen, and epinephrine (all of which require GPIIb/IIIa), but normal ristocetin response (ristocetin uses GPIb, not GPIIb/IIIa). Giant platelets on blood smear are characteristic of Bernard-Soulier.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.