classification

Last reviewed 01/2018

Three types of von Willebrand's disease are recognised on the basis of ristocetin activity and other tests:

• type I, the the classic type described by von Willebrand in 1926, where the von Willebrand factor is functionally normal but present at low levels
• type II, a broad spectrum of diseases in which bleeding time is prolonged in almost all cases. vWF levels may increase under some conditions - like stress or pregnancy, correcting the bleeding time
• type IIa - both plasma and platelet samples lack the intermediate and high molecular weight vWF multimers; platelets do not aggregate with ristocetin
• type IIb - plasma lacks the highest molecular weight vWF multimers; platelets aggregate in response to low dose ristocetin
• type III is inherited as an autosomal recessive trait. Homozygous individuals have severe bleeding problems related to marked reduction of all von Willebrand's factor parameters and of Factor VIII