Which statement best describes type II N von Willebrand disease?

Which statement best describes type II N von Willebrand disease?

• A. FVIII binding to VWF is defective
• B. vWF antigen synthesis is defective
• C. ristocetin binding is defective
• D. platelet aggregation is defective

Answer: (A)

The key idea is that type 2N von Willebrand disease involves a defect in the ability of von Willebrand factor to bind factor VIII. Because VWF normally protects and stabilizes FVIII in circulation, a defective FVIII–VWF interaction leads to low circulating FVIII activity even when VWF itself is present and can function for platelet adhesion. That’s why this type presents with reduced FVIII levels despite typically normal VWF antigen and normal ristocetin-induced platelet function. If the problem were defective VWF synthesis, you’d expect low VWF antigen levels. If ristocetin binding were defective, platelet adhesion would be impaired (seen in other subtypes). If platelet aggregation were broadly defective, that would point to other types that disrupt VWF–GPIb interactions. The isolated defect in FVIII binding best fits type 2N.

The key idea is that type 2N von Willebrand disease involves a defect in the ability of von Willebrand factor to bind factor VIII. Because VWF normally protects and stabilizes FVIII in circulation, a defective FVIII–VWF interaction leads to low circulating FVIII activity even when VWF itself is present and can function for platelet adhesion. That’s why this type presents with reduced FVIII levels despite typically normal VWF antigen and normal ristocetin-induced platelet function.

If the problem were defective VWF synthesis, you’d expect low VWF antigen levels. If ristocetin binding were defective, platelet adhesion would be impaired (seen in other subtypes). If platelet aggregation were broadly defective, that would point to other types that disrupt VWF–GPIb interactions. The isolated defect in FVIII binding best fits type 2N.