Factor VIII activity may be reduced in von Willebrand disease in which context?

• A. In some types of von Willebrand disease
• B. In all types
• C. Only in Bernard-Soulier
• D. Never

Answer: (A)

Factor VIII depends on von Willebrand factor for protection and stability in plasma. When VWF is deficient or dysfunctional, there is less VWF available to carry and shield FVIII, so its activity in clotting can be reduced. This occurs in several VWD subtypes, such as those with quantitative VWF deficiency (less VWF means less FVIII stabilization) and a subtype where VWF cannot properly bind FVIII, leading to lower FVIII activity despite VWF levels. In contrast, Bernard-Soulier is a platelet receptor defect, not a problem with VWF levels or its ability to stabilize FVIII, so Factor VIII activity is not typically reduced there. So Factor VIII activity may be reduced in certain forms of von Willebrand disease, depending on the specific VWF defect.