[Molecular defects of coagulation factors and of the fibrinolytic system associated with thromboembolism]

Some molecular defects of components of the coagulation or fibrinolytic system are associated with thromboembolism. One possibility is that physiologic inhibitors of the coagulation system have an abnormal function e.g. protein C, protein S, antithrombin III and cofactor II of heparin. Also a hindered activation of the fibrinolytic system may predispose to thrombosis; the impaired activation may be due to deficient synthesis and/or release of tissue-plasminogen activator, an increased level of its inhibitor or a functional defect of the plasminogen molecule. A few cases of congenital dysfibrinogenemia have been described in which the functional defects of the molecule are held responsible for recurrent thrombosis. An acquired thrombotic disorder is due to the presence of immunoglobulins which prolongs phospholipid-dependent coagulation by binding to epitopes of some phospholipids. This so-called lupus anticoagulant was originally described in patients with systemic lupus erythematosus but is a misnomer as it is more frequently encountered in patients without lupus.