Abnormal Fibrin Monomer Polymerization In Patients With Lupus Erythematosus Systemicus (LES)

Fibrin monomer polymerization was studied in 10 out of 44 patients with LES, selected for their prolonged thrombin time (patients 24.6 ± 1.9 sec; normal controls 15.0 ± 0.5 sec). One of these patients had also a lupus-like blood clotting inhibitor. The level of fibrinogen measured as thrombin clottable protein was 407.5 ± 62.7 mg/dl, and as heat precipitable protein 325.8 ± 49.3 mg/dl. Fibrin monomer polymerization with thrombin assayed as the increment in O.D., showed in 5 patients a delay of two minutes compared to the normal controls. Under the same condition the O.D. did not show any change in 2 other patients. Purified IgG obtained from plasma of these patients had an inhibitory effect on the polymerization of human and bovine fibrinogen. IgG from normal plasma had no effect in this system. The fibrinogen of these patients had more anodic mobility than normal fibrinogen when studied by two-dimentional immunelectrophoresis. Factor XIII activity, euglobulin lysis time, and serum FDP gave results within normal range. We conclude that the prolonged thrombin time observed in some patients with LES seems to be the consequence of an abnormal fibrinogen function related to an interference by their own IgG.