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 (IMW) 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
|
