VWF and von Willebrand disease 3: VWF−/− mice have ~20% of normal circulating factor VIII (a phenotype which parallels the decreased levels of circulating FVIII in humans with Type 3 VWD, typically ~1–20%) which could exacerbate bleeding, but would be expected to support a degree of thrombin generation not present in FIX−/− or FVIII−/− mice18,37–39.