Type 2 Von Willebrand disease

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1 type 2

1.1 type 2a
1.2 type 2b
1.3 type 2m
1.4 type 2n (normandy)





type 2

type 2 vwd (15-30% of cases) qualitative defect , bleeding tendency can vary between individuals. 4 subtypes exist: 2a, 2b, 2m, , 2n. these subtypes depend on presence , behavior of underlying multimers.


type 2a

the vwf quantitatively normal qualitatively defective. ability of defective von willebrand factors coalesce , form large vwf multimers impaired, resulting in decreased quantity of large vwf multimers , low rcof activity. small multimer units detected in circulation. von willebrand factor antigen (vwf:ag) assay low or normal.


type 2b

this gain of function defect. ability of qualitatively defective vwf bind glycoprotein ib (gpib) receptor on platelet membrane abnormally enhanced, leading spontaneous binding platelets , subsequent rapid clearance of bound platelets , of large vwf multimers. thrombocytopenia may occur. large vwf multimers reduced or absent circulation.


the ristocetin cofactor activity low when patient s platelet-poor plasma assayed against formalin-fixed, normal donor platelets. however, when assay performed patient s own platelets (platelet-rich plasma), lower-than-normal amount of ristocetin causes aggregation occur. due large vwf multimers remaining bound patient s platelets. patients subtype unable use desmopressin treatment bleeding, because can lead unwanted platelet aggregation , aggravation of thrombocytopenia.


type 2m

type 2m vwd qualitative defect of vwf characterized decreased ability bind gpib receptor on platelet membrane , normal capability @ multimerization. vwf antigen levels normal. ristocetin cofactor activity decreased , high molecular weight large vwf multimers present in circulation.


type 2n (normandy)

this deficiency of binding of vwf coagulation factor viii. vwf antigen test normal, indicating normal quantity of vwf. ristocetin cofactor assay normal. assay coagulation factor viii revealed marked quantitative decrease equivalent levels seen in hemophilia a. has led vwd type 2n patients being misdiagnosed having hemophilia a.








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