Type 2B Hiroshima: a variant of von Willebrand disease characterized by chronic thrombocytopenia and the presence of all von Willebrand factor multimers in plasma.

Type 2B von Willebrand disease (vWD) is a von Willebrand factor (vWF) subtype with increased binding affinity for platelet glycoprotein (GP) Ib and is characterized by increased ristocetin-induced platelet agglutination at low concentrations of ristocetin. Usually there are no high molecular weight multimers of vWF, and platelet counts are within normal ranges in patients with type 2B vWD. We identified a variant of type 2B vWD showing the full range of vWF multimers in plasma accompanied by thrombocytopenia, which seemed to be caused by circulating platelet aggregation. Since the A1 domain and surrounding region of vWF alleles, in which mutation sites are known to be clustered in type 2B vWD, appeared normal on nucleotide sequencing, this increased binding affinity of vWF for GPIb may be due to a novel mechanism differing from that which usually underlies type 2B vWD.