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Hematology Center
vWF

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1. Common variants of von Willebrand's disease
2. Common questions about vWD
3. Replacement therapy in vWD

Type I
> autosomal dominant
> normal or reduced factor VIIIc & vWF antigen
> normal multimeric analysis
> normal or reduced ristocetin cofactor activity
> normal or reduced ristocetin-induced platelet aggregation
> normal or reduced vWF in platelets
> DDAVP responsive


Type 2A
> autosomal dominant
> normal or reduced factor VIIIc & vWF antigen
> large & intermediate sized multimers are absent
> reduced ristocetin cofactor activity
> reduced ristocetin-induced platelet aggregation
> absence of large & intermediate sized multimers of vWF in platelets
> DDAVP does not rise functional vwf!


Type 2B
> autosomal dominant
> normal or reduced factor VIIIc & vWF antigen (But increased affinity of vWF antigen for platelets)
> large multimers are absent
> normal or reduced ristocetin cofactor activity
> INCREASED ristocetin-induced platelet aggregation
> vWF in platelets are normal
> DDAVP causes variable response. In some cases in might cause intravascular platelet aggregation & thrombocytopenia



Type 2C
> autosomal recessive
> normal or reduced factor VIIIc & vWF abtigen
> large multimers are reduced; small multimers increased; aberrant banding
> reduced ristocetin cofactor activity
> reduced ristocetin-induced platelet aggregation
> DDAVP responsive


Type 3
> autosomal recessive
> reduced factor VIIIc & vWF antigen
> variable abnormalities in the multimeric analysis
> reduced ristocetin cofactor activity & markedly reduced ristocetin-induced platelet aggregation
> no response to DDAVP



Platelet-Type
> autosomal dominant
> normal or reduced factor VIIIc & vWF antigen (But increased affinity of vWF antigen for platelets)
> Large multimers are absent because of their consumption by platelets
> reduced or normal ristocetin cofactor activity
> With respect to ristocetin-induced platelet aggregation, there is HYPERAGGREGATION with patients platelets, normal plasma & low concentrations of ristocetin
> vWF in platelets are normal
> DDAVP may produce intravascular platelet aggregation & thrombocytopenia. Same could happen with vWF transfusion




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What is ristocetin?
An antibiotic that induces platelet agglutination. This process is dependent on the binding of vWF to the platelet. This process occurs only in the presence of ristocetin!


What is ristocetin cofactor activity?
A quantitative technique for estimating the functional property of vWF in the plasma


What is ristocetin-induced platelet aggregation?
It is a qualitative test that involves titrating ristocetin concentrations to the concentration required to induce aggregation (besides vWD, Bernard-Soulier Syndrome also alters this property)


Which type of vWD is associated with thrombocytopenia?
Type 2B (thrombocytopenia may also occur after DDAVP administration, or with pregnancy).
The Platelet type is also associated with mild thrombocytopenia


Which type of vWD is most severe?
Type 3 vWD (marked deficiencies of both vWF & factor VIII, absence of vWF in both endothelial cells & platelets)


Which type is also called pseudo-vWD?
The platelet type! It is actually caused by a defect in glycoprotein Ib which is the platelet receptor for vWF. The result is "consumption" of vWF, especially the large mutlimers.



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Replacement therapy in vWD
Humate-P dose schedule by manufacturer (CENTEON)
Stimate??sal Spray dose schedule by manufacturer (CENTEON)



1. Humate-P
2. Koate-HP
3. Croprecipitate
use 1 bag/10 kg QD
4. Vasopressin
Type I vWD only (see the nasal spray form by CENTEON)



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Overall treatment strategy:

If Type I VWD Then can try DDAVP First

However, patients may require further factor replacement given that effects of DDAVP are transient with peak effects about 1-2 hours following administration & decline over the next 4-6 hours, roughly.

Factors available at this time:

1. Humate-P 2000 U Q 12 then QD
(see manufacturer's link for a different approach to Humate-P dosing)
2. Alphanate 2000 U Q 12 then QD
3. Koate-HP 2000 U Q 12 then QD

If none of the abve are avaiable, use cryoprecipitate 1 bag/kg/day

the length of administration depends on the severity of bleeding & or procedure planned.

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