Infection and inflammation as risk factors for thrombosis and atherosclerosis.

Severe infection and inflammation almost invariably lead to hemostatic abnormalities, ranging from insignificant laboratory changes to gross activation of coagulation that may result in localized thrombotic complications or systemic intravascular fibrin deposition. Systemic inflammation results in activation of coagulation, due to tissue factor-mediated thrombin generation, downregulation of physiological anticoagulant mechanisms, and inhibition of fibrinolysis. Proinflammatory cytokines, immune cells, and the endothelium play a central role in the differential effects on the coagulation and fibrinolysis pathways. Vice-versa, activation of the coagulation system may importantly affect inflammatory responses by direct and indirect mechanisms. Similar mechanisms appear to play a role in the development of atherosclerosis and related arterial thrombosis. Apart from the general coagulation response to inflammation associated with severe infection, specific infections may cause distinct features, such as hemorrhagic fever or thrombotic microangiopathy.