Which of the following may be associated with thrombotic events?

Thrombotic events are often linked to conditions that disrupt the normal regulation of coagulation and fibrinolysis in the body. Decreased protein C is crucial in this context, as protein C is an important plasma protein that plays a significant role in controlling blood coagulation. When protein C levels are reduced, there is less activation of the protein C pathway, which normally helps to inactivate factors Va and VIIIa—factors that promote clot formation. This imbalance can lead to a hypercoagulable state, significantly increasing the risk for the formation of thrombi, or blood clots, within the vasculature.

In contrast, increased fibrinolysis would typically work to break down clots, reducing the chances of thrombotic events. Afibrinogenemia, a condition characterized by a lack of fibrinogen, would also hinder the formation of clots entirely, not promoting them. Immune thrombocytopenic purpura (ITP) primarily leads to a decrease in platelets rather than promoting thrombotic events, as it is predominantly associated with bleeding risks due to lower platelet counts. Thus, decreased protein C is most directly associated with an increased risk of thrombotic events.