Dos-Santos JCK, Silva-Filho JL, Judice CC, et al. - In view of the observations that the pathogenesis of Plasmodium vivax malaria involves endothelial cell activation as a key process and that endothelial cell activation in several diseases classically involves platelets, researchers here examined role of platelets in the context of vivax malaria. From infected peripheral blood, the retrieved platelets were non-activated when analyzed by flow cytometry, but displayed higher mean volume and significantly reduced counts. Higher levels of circulating factors were noted in correlation with platelet activation (especially soluble CD40L), thrombopoiesis and endothelial cell activation in infected patients. Further, pair-wise correlation and clustering analysis revealed a subgroup of patients indicating significant correlations between markers of platelet and endothelial activation in a pattern different from that of endemic controls. Collectively, the results suggest that platelets play a role in endothelial cell activation in vivax malaria and imply a heterogeneous host response in the setting of uncomplicated disease.