Von Willebrand disease type 2B is characterised by a gain-of-function mutation in vWF that causes it to bind platelet GPIb spontaneously. The expected laboratory findings include:

• A Prolonged PT, normal aPTT, normal platelet count
• B Normal bleeding time, normal vWF antigen, low factor VIII activity
• C Thrombocytopenia, loss of high-molecular-weight vWF multimers, increased ristocetin-induced platelet aggregation at low doses ✓
• D Prolonged aPTT only, normal vWF antigen, normal ristocetin cofactor

Explanation

vWD type 2B is caused by gain-of-function mutations in the GPIb-binding domain of vWF, causing spontaneous platelet binding and clearance of platelets and high-molecular-weight multimers in vivo. This leads to mild-moderate thrombocytopenia, loss of HMW multimers, and paradoxically enhanced ristocetin-induced platelet aggregation even at low ristocetin doses (unlike type 2A where there is loss of HMW multimers but decreased RIPA). Type 2B is treated with vWF concentrate (NOT DDAVP, which releases more abnormal vWF).

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.