Increased factor VIII/vWf levels in patients with reduced platelet number

Summary Factor VIII/von Willebrand factor (VIII/vWf) related properties were studied in twenty six patients with thrombocytopenia. Fifteen patients were affected by idiophatic thrombocytopenic purpura (ITP) and 11 patients by thrombocytopenia of a different nature or non-ITP (n-ITP). All patients showed an enhancement of platelet associated IgG (PAIgG). A significant increase of factor VIII ristocetin cofactor (VIII R: RCoF) and factor VIII related antigen (VIII R: Ag) was found in ITP patients while normal values were observed for factor VIII coagulant (VIII: C). All factor VIII/vWf components, on the contrary, were increased in n-ITP group with a prevalence of VIII R: RCoF as observed in ITP group even though with lower mean values. Multimeric analysis of VIII/vWf demonstrated a higher concentration of all multimeric components, with major representation of higher molecular weight multimers (HMWM) in patients of both groups.Two patients were studied before and after improvement in platelet count. A decrease of vWf related properties (VIII R : RCoF and VIII R : Ag) concomitant with the increase in platelet count was found. In n-ITP patients a statistical correlation between VIII R : RCoF and PAIgG was also observed while no correlation was found between other factor VIII/vWf components and PAIgG both in ITP and n-ITP patients.