Von Willebrand Disease

• Most common coagulopathy (1% population)
• The classic and most common form (Type 1) is mild, with few to no symptoms
• Inherited autosomal dominant, so usually have (+) FHx
• Many different types, vWF levels may be low or normal but nonfunctional

Presentation

• Presents with mucocutaneous bleeding (epitaxis, menorrhagia, bleeding gums, bruising, bleeding with IV’s…)
• Rare to get hemarthrosis
• Often totally asymptomatic
• Diagnosis often made based on a carefully obtained FHxof bleeding, with supportive lab values

vWF function

• vWFserves as an essential link in binding the platelets to the vessel wall (like glue). Therefore, if it is absent, you can’t get the initial platelet clot
• It also is a carrier protein for Factor 8 and protects it. Therefore, if it is low, Factor 8 will be low, and the PTT will be prolonged
• It is an acute phase reactant, and thus can have normal levels of vWF in an ill patient who would otherwise have low levels

Labs, Type 1 vWF

• Prolonged bleeding time (PFA-100)
• Perhaps prolonged PTT, depending on factor VIII level
• Normal PT and CBC
• Low vWF level
• Abnormal Ristocetin test (functional test) - in normal blood, vWF is attached to platelets and ristocetin will bind the vWF and agglutinate the sample. in vWD, there is no vWF, so no agglutination.
• Blood Type “O” assoc with lower levels of vWF

Types of vWD

vWF is synthesized in multimers that are large to small in size. The largest ones work the best. vWF then either binds to platelets to make the initial clot, or to Factor VIII to support and protect it.

• Type 1 (80%) –low levels of all size multimers
• 2A –No large multimers (which work the best), so more bleeding than Type 1
• 2B –Large multimers bind platelets and both get taken out in the spleen, so have both low vWF and platelet levels
• 2M –vWF can’t bind platelets well
• 2N –vWF can’t bind Factor VIII well
• 3 –Completely absent levels of vWF –homozygous form; <5% Factor VIII levels as well

Treatment

• Observation if not clinically evident
• DDAVP - stimulates release of factor VIII and vWF from cells; Last only few hours, so use 15–30 min before dental or other procedures, and Q12-24 hrs prn bleeding
• FVIII-vWF infusion
• OCP for menorrhagia
• Aminocaproic acid for mucosal bleeds

CHLA Board Review 2005