FURTHER EVIDENCES OF VON WILLEBRAND FACTOR INVOLVEMENT IN THROMBOTIC THROMBOCYTOPENIC PURPURA (TTP)

Laboratory findings of TTP include severe thrombocytopenia and marked anemia due to intravascular hemolysis. The pathogenesis of the thrombocytopenia is poorly understood. Possible mechanisms include the presence of a platelet aggregating factor (JCI 76:1330, 1935), a calcium dependent protease (Blood 63:310a, 1986), abnormal prostaglandin production or metabolism, and an excessive consumption of high molecular weight forms of von Uillebrand factor (VUF). Von Willebrand factor proteins from 12 patients (pts) diagnosed as having TTP were studied. They include 8 females and 4 males; nine were studied during the acute presentation and seven pts also during the remission period. Three pts died during the acute event. None of the pts had a recurrence. Control subjects include both normal individuals and thrombocytopenic pts due to a variety of underlying diseases including marrow aplasia and immune thrombocytopenia, but excluding pts with DIC or suffering infection. Plasmas were tested for VWF antigen and Ristocetin Cofactor (RiCof) activity. The electrophoretic mobility (CIE) of VWF:Ag was also assessed and the ratio VWF:RiCof to VWF:Ag was determined. Statistical analysis including p values will be reported. Results:

These results suggest that during the acute event there is an excessive consumption of large VWF multimers and the ratio VWF:RiCof/VWF:Ag could be used to corroborate the diagnosis of TTP and by doing sequential measurements to monitor the response to therapy.