Fibrin monomers are increased in which of the following conditions?

Fibrin monomers are increased in disseminated intravascular coagulation (DIC) due to the pathological activation of the coagulation cascade. In DIC, widespread activation of clotting factors occurs, leading to the formation of fibrin clots throughout small blood vessels. This excessive coagulation depletes clotting factors and platelets, resulting in simultaneous fibrinolysis, where the body attempts to break down the clots. As fibrinogen is converted to fibrin, the resulting fibrin monomers are released into circulation. The presence of increased fibrin monomers serves as an indicator of the ongoing coagulation and subsequent breakdown of fibrin, characteristic of DIC.

In contrast, primary fibrinolysis, factor VIII deficiency, and fibrinogen deficiency do not typically result in elevated fibrin monomers. Primary fibrinolysis involves increased fibrinolysis without prior significant clot formation, while factor VIII deficiency affects the coagulation cascade's ability to promote sufficient clot formation. Fibrinogen deficiency leads to inadequate production of fibrin and resultant fibrin monomers, further differentiating it from the state seen in DIC.