Von Willebrand Disease (VWD): Diagnostic Differentiation ofPseudo, Mild, Moderate to Severe VWD Type 1 and 2 by a DDAVPChallenge Test on Top of the ISTH Classification

A complete set of FVIIIl:C and von Willebrand factor ristocetine cofactor, collagen binding and antigen (VWF:RCo. VWF:CB, VWF:Ag) and Ristocetine Induced Platelet Agglutination (RIPA) and VWF multimeric analysis in a low resolution gel is mandatory to diagnose all variants of Von Willebrand Disease (VWD) according to ISTH (International Society on Thrombosis and Haemotasis) criteria. The response to DDAVP of VWF parameters is normal in pseudo-VWD, and mild VWD type 1 Bloodgoup O, but restrictive in carriers of recessive type 1 and 3 VWD. The response to DDAVP is restricted in pronounced VWD type 1 and 1/2E, transiently good in mild type 2A group II, good for VWF:CB but poor for VWF:RCo in VWD 2M, poor for VWF:RCo and VWF:CB in 2A group I, 2B, 2C and 2D, very poor in recessive VWD severe type 1m and absent in VWD type 3. VWF multimers in a low resolution gel are normal in VWD type 1 and 2M, but RIPA is normal in dominant VWD type 1 and decreased in dominant VWD type 2M. Dominant VWD 1/2E due to mutations in the D3 domain of VWF result in defective multimerization, defective secretion and/or increased clearance of VWF. The triplet structure of each band and loss of large VWF multimers is charateristic for VWD type 2A and 2B due to increased proteolysis of each VWF band. Mild to moderate VWD 2A group II patients have normal FVIII:C and VWF:Ag, decreased VWF:RCo and VWF:CB, normal RIPA and transient correction of BT, FVIII:C, VWF parameters, and large multimers for a few hours post-DDAVP. Severe VWD 2A group I patients have low VWF:Ag and very low levels for VWF:RCo and VWF:CB, no RIPA and poor response of functional VWF:RCo and VWF:CB. VWD 2B is featured by loss of large VWF multimers due to increased proteolysis caused by increased interaction of platelets and mutated VWF.