- Most common inherited bleeding disorder worldwide.
- von Willebrand factor is synthesized in endothelium and megakaryocytes and forms a large multimer to carry factor VIII and anchors platelets to subendothelium as bridge between platelets.
- Inheritance - autosomal dominant
- Clinical features - mucocutaneous bleeding; epistaxis, menorrhagia etc.
- Type I: Partial quantitative deficiency of vWF (70% of cases, mild-moderate disease)
- Type II: Qualitative deficiency of vWF (25% of cases, mild to moderate disease)
- Type III: Total or near total deficiency of vWF (5% of cases, severe disease)
- Prolonged aPTT in 50% of cases (due to low factor VIII). Normal aPTT does not rule out vWD
- Normal PT
- Prolonged bleeding time; DO NOT PERFORM. This is replaced by PFA-100 which is not available at MUSC (assess platelet function)
- Send vWF antigen level and activity, Factor VIII, Ristocetin cofactor assay, vWF multimeric analysis
- DDAVP: Useful in mild cases (Type I), contraindicated in Type IIB, not useful in Type III. See hemophilia section for dosing details
- vWF replacement therapy: Humate-P (recombinant product): The dosage of Humate-P® required (IU VWF:RCo) = body wt. (kg) x desired % increase in VWF activity ÷ 1.5. As a rule, 40-80 IU VWF:RCo per kg body weight are given every 8-12 hours. The dose should be adjusted according to the type of VWD and the extent and location of the bleed.
- Adjunctive therapy with Amicar (see hemophilia section)