Von Willebrand's disease

Question 1

Define

Answer 1

Functions of VWF in clotting:
VWF is a glycoprotein involved in blood clotting

(1) To bring platelets into contact with exposed subendothelium, acts as an adhesive bridge between GP-Ib plt receptors and damaged subendothelium collagen IV of vessels
(2) To make platelets bind to each other
(3) To bind to factor VIII, protecting it from

degradation in the circulation

DEFINITION: bleeding disorder which may present with mucocutaneous bleeding (mouth, epistaxis, menorrhagia), increased bleeding after trauma and easy bruising

There are THREE types of von Willebrand disease:

Type 1 - the von Willebrand factor works well but there isn’t enough of it

Type 2 - there are normal levels of von Willebrand factor but it is abnormal and doesn’t function correctly

Type 3 - there is NO von Willebrand factor

Question 2

Causes

Answer 2

abnormities in expression or function of VWF

Usually AUTOSOMAL DOMINANT (occasionally recessive) Also acquired forms

Risk factors:

vWF is an adhesive bridge between platelets and the damaged subendothelial collagen

vWF also binds to factor VIII and prevents its degradation

Question 3

Epidemiology

Answer 3

most common hereditary coagulopathy in humans, prevalence as high as 1-2%

↘ Most pts have mild disease

↘ More common in females

↘ More severe in blood type O

Question 4

Symptoms

Answer 4

• Easy bruising
• Epistaxis - hard to stop
• Prolonged bleeding from gums after dental procedures
• Heavy or prolonged menstrual bleeding
• Blood in stools
• Blood in urine
• Heavy bleeding from a cut or other accident

Signs:

Anaemia, signs of liver disease

Unusual bruising or recent bleeding

Question 5

Investigations

Answer 5

Bleeding time - HIGH

APTT - HIGH

Factor VIII - LOW

vWF - LOW

Ristocetin cofactor - reduced platelet aggregation by vWF in the presence of ristocetin