Clinically patients suffer from mucosal bleeding and bleeding post-op such as a dental extraction or after injury or higher than usual menstrual bleeding. Aspirin should be avoided. Tranexamic acid may be used.
About
- Commonest bleeding disorder with platelet dysfunction and clotting factor deficiency
- Inheritance is usually AD but other forms including AR also can occur. 22 types in total
- Unlike Haemophilia which affects males only this affects both sexes equally
- The gene for vWF is on Chromosome 12 - with several mutations and phenotypes
- Clinically resembles a mild Haemophilia A
Aetiology
- vWF acts as a sort of bridge to bind platelets to the collagen of the vessel wall.
- One end of the vWF molecule attaches to the GP1b receptor on the platelet surface and the other to collagen.
- The other platelet receptor GP1a binds directly to collagen.
- Once bound the platelet releases ADP, TXA2 and Serotonin.
- The other role for vWF is to act as a sort of molecular anchor and stabilise Factor VIII.
- vWF is synthesised by endothelial cells and megakaryocytes.
Investigations
- Prolonged bleeding time (platelet dysfunction) but platelet count normal
- Prolonged APTT (Factor VIII deficiency)
- Normal PT
- Low VIII:vWF and Low Factor VIII:C
- Ristocetin fails to cause platelet aggregation in vWD
Classification
- Type 1: Mild AD inheritance with epistaxis, bruises and mild GI bleeds
- Type 2: Mild AD inheritance with epistaxis, bruises and mild GI bleeds
- Type 3: More severe but not as severe as Haemophilia A
Management
- Avoid NSAIDS and IM injections
- DDAVP (desmopressin) which stimulates the endothelium to release vWF
- Factor VIII:vWF concentrates may be given prior to surgery especially with Type 3 disease