Makindo Medical Notes.com

Related Subjects: Blood Products - Platelets

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