INCREASED P-SELECTIN PLASMA-LEVELS IN PATIENTS WITH THROMBOTIC THROMBOCYTOPENIC PURPURA

Background. Thrombotic thrombocytopenic purpura (TTP) is a rare vascul ar disorder of unknown etiology. There is evidence to support the hypo thesis that platelets and endothelium play a pivotal pathogenetic role . Immunological assays for plasma thrombomodulin and P-selectin levels have recently been made available and they allow simple evaluation of endothelial damage and endothelial/platelet activation, respectively. In this study, we measured the plasma levels of thrombomodulin, P-sel ectin and von Willebrand factor in 9 TTP patients during active diseas e and at the time of complete remission (CR). Methods. Thrombomodulin, P-selectin and von Willebrand factor were measured by enzyme immunoas say. Results. Mean thrombomodulin and von Willebrand factor plasma val ues were always within the normal range. P-selectin plasma levels, bot h in the active phase of the disease and in CR (median 312 and 185 ng/ mL, respectively), were significantly higher than in normal controls ( mean 96+/-35 ng/mL, median 88 ng/mL; p < 0.05). However, the mean valu e of P-selectin in CR (median 185 ng/mL) was significantly lower than that observed at diagnosis (p < 0.05). in addition, an inverse relatio nship between P-selectin plasma levels and platelet count (r = -0.526; p = 0.03) was observed. Conclusions. These findings suggest that acti vation of platelets and/or endothelium may play a relevant role in the pathogenesis of TTP.