Von Willerbrand's Disease

Question 1

Define von Willerbrand’s disease

Answer 1

Inherited deficiency in von Willebrand factor

Autosomal dominant
• Type 1 – partial deficiency
• Type 2 –abnormal function, includes IIA, IIB, IIN, IIM

Autosomal recessive
• Type 3 – complete deficiency
There is also a rare acquired form of vWD due antibody formation to vWF

Question 2

What are the causes/risk factors of on Willerbrand’s disease?

Answer 2

Defective interaction between vWF and vessel wall -> impaired primary haemostasis
• Family history
• Consanguinity

Question 3

What are the symptoms of on Willerbrand’s disease?

Answer 3

• Easy bruising
• Epistaxis
• Prolonged bleeding e.g. after minor trauma to skin or mucous membranes
• Severe post-operative haemorrhage
• Heavy bleeding e.g. after oral surgery (tooth extraction, tonsillectomy)
• Menorrhagia

Question 4

What are the signs of of Willerbrand’s disease?

Answer 4

• Purpura

* Ecchymoses

Question 5

What investigations are carried out for on Willerbrand’s disease?

Answer 5

• FBC - results usually normal with VWD, except in type 2B, when the platelet count may be reduced. There may be anemia secondary to excessive bleeding.
• PT - normal
• TT - normal
• APTT - normal; Prolonged if Factor VIII deficiency
• Factor VIII Assay - may be reduced; function may be reduced.
• Bleeding Time - prolonged (Not used any more) –not very sensitive.
- Newer tests, notably the platelet function analyser (PFA100), have better testing characteristics than the bleeding time, but are still not sensitive enough to exclude all cases of VWD.
• VWF Antigen - reduced; diagnostic for VWD if <0.30 IU/mL
- VWF Function Assay: Ristocetin cofactor and collagen binding assays.
- Values decrease in parallel to VWF antigen, except in type 2 disease.
- The ristocetin cofactor assay and collagen binding assay both measure function of VWF, and results are normally broadly consistent.
- Ratio of VWF function to VWF antigen <0.6 is consistent with a diagnosis of type 2 VWD

**Because VWF is so variable in a patient, abnormal tests should be repeated and 2 concordant results obtained for definitive diagnosis.