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) subty pe with increased binding affinity for platelet glycoprotein (GP) Ib and is characterized by increased ristocetin-induced platelet agglutination at lo w 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 r ange of VWF multimers in plasma accompanied by thrombocytopenia, which seem ed to be caused by circulating platelet aggregation. Since the Al domain an d surrounding region of VWF alleles, in which mutation sites are known to b e 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. (C) 1999 The Japan ese Society of Hematology.