Table 1: classification of VWD
TYPE	Description	Comments	Inheritance
1	Partial quantitative deficiency of VWF	Includes VWF mutations causing rapid VWF clearance (e.g. VWF Vicenza) and requires function: antigen ratio >0.6	Mostly autosomal dominant inheritance when VWF < 0.3 IU/ml. Mutations of VWF in kindred with levels > 0.3 IU/ml show variable penetrance
2	Qualitative VWF defects
2A	Decreased VWF-dependent platelet adhesion with selective deficiency of high-molecular-weight multimers	Some controversy exists regarding classification of VWF mutations associated with subtle reductions in HMW multimers	Mostly autosomal dominant
2B	Increased affinity for platelet GPIb	Should be distinguished from PT-VWD, using either platelet agglutination tests or genetic testing. Cases with normal VWF multimer and platelet count have been described	Autosomal dominant
2M	Decreased VWF-dependent platelet adhesion without selective deficiency of HMW multimers	This also includes defects of VWF collagen binding. May be combined quantitative/qualitative defect	Autosomal dominant
2N	Markedly decreased binding affinity for FVIII	Should be distinguished from mild haemophilia A	Reduced VWF: FVIII binding defects are more commonly identified in a compound heterozygote state with a VWF null allele rather than the classical homozygous form
3	Virtually complete deficiency of VWF	Equivalent to < 0.03 iu/ml in most assays	Autosomal recessive, frequent null VWF alleles. Bleeding symptoms in 26 - 48% of obligate carriers
VWD, von Willebrand disease; PT-VWD, platelet type pseudo-VWD; VWF, von Willebrand factor; VWF, VWF gene; FVII, factor VIIIGPIb, glycoprotein Ib; HMW, high molecular weight