| Type | Description |
|---|---|
| 1 | Partial quantitative VWF deficiency • The most common form (50 to 70% of cases) • Several subtypes depending on intra-platelet VWF content • Difficult to diagnose: overlap between VWF levels in patients and the normal population • VWF levels between 10 and 50% • Corresponding reduction in VWF antigen (VWF:Ag) and in ristocetin cofactor activity (VWF:RCo) Ratio of VWF:RCo/VWF:Ag > 0.7 • Dominant transmission with varying expression and penetrance |
| 2 | Qualitative VWF deficiency • Abnormal interaction between VWF and platelets |
| 2A | Deficient platelet adhesion dependent on VWF associated with selective deficiency of high molecular weight (HMW) multimers • Abnormal interaction of VWF with platelets; decreased affinity of VWF for platelets due to absence of high molecular weight and intermediate molecular weight multimers • Ratio of VWF:RCo/VWF:Ag < 0.7 • Dominant transmission with varying expression and penetrance |
| 2B | High affinity of VWF for platelet glycoprotein Ib • Adsorption of HMW multimers on platelets resulting in fluctuating thrombocytopenia • Dominant transmission with varying expression and penetrance |
| 2M | Deficient VWF-dependent platelet adhesion with no selective deficiency in HMW multimers • Reduced affinity of VWF for platelets not associated with a multimerisation abnormality • Dominant transmission with varying expression and penetrance |
| 2N | Marked deficiency in VWF binding to factor VIII • Diagnosis through study of VWF binding to FVIII • Normal levels of VWF (VWF:Ag and VWF:RCo) • Factor VIII deficit with ratio of FVIII:C/VWF:Ag < 0.5 • Recessive autosomal transmission |
| 3 | Complete quantitative VWF deficiency • The rarest form: 1 to 3% of patients • Subjects homozygous or composite heterozygous • VWF undetectable • Extremely low levels of factor VIII (< 10%) • Autosomal recessive transmission |
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