Which laboratory finding is most consistent with von Willebrand disease?

Which laboratory finding is most consistent with von Willebrand disease?

• A. Isolated prolonged prothrombin time.
• B. Isolated prolonged partial thromboplastin time.
• C. Decreased bleeding time.
• D. Increased platelets.

Answer: (B)

Von Willebrand disease affects the way platelets stick to damaged vessels and also stabilizes factor VIII in the circulation. Because factor VIII is part of the intrinsic coagulation pathway, a deficiency or dysfunction of von Willebrand factor can lengthen the intrinsic pathway, leading to a prolonged aPTT. The prothrombin time (which measures the extrinsic pathway) is typically normal in vWD, and platelet counts are usually normal, though bleeding time can be prolonged due to defective platelet adhesion. Therefore, an isolated prolongation of the aPTT best fits von Willebrand disease.

Von Willebrand disease affects the way platelets stick to damaged vessels and also stabilizes factor VIII in the circulation. Because factor VIII is part of the intrinsic coagulation pathway, a deficiency or dysfunction of von Willebrand factor can lengthen the intrinsic pathway, leading to a prolonged aPTT. The prothrombin time (which measures the extrinsic pathway) is typically normal in vWD, and platelet counts are usually normal, though bleeding time can be prolonged due to defective platelet adhesion. Therefore, an isolated prolongation of the aPTT best fits von Willebrand disease.