SummaryCoagulation and fibrinolytic activities were studied in 18 subjects with Behçet's disease and compared with results from 14 matched control patients suffering from sero-negative arthritis. Significantly higher plasma concentrations (median and range) were found in Behçet's patients for the following variables: fibrinogen 3.7 (1.7-6.9) vs 3.0 (2.0-5.1) g/1, p <0.05; von Willebrand factor antigen, 115 (72-344) vs 74 (60-119)%, p <0.002; plasminogen activator activity (106/ECLT2) 219 (94-329) vs 137 (78-197) units, p <0.002; tissue plasminogen activator inhibitor (t-PA-I) activity, 9.1 (5.5-19.3) vs 5.1 (1.8-12.0) IU/ml, p <0.002; and PAI-1 antigen, 13.9 (4.5-20.9) vs 6.4 (2.4-11.1) ng/ml, p <0.002. Protein C antigen was significantly lower: 97 (70-183) vs 126 (96-220)%, p <0.02. No differences were observed in antithrombin III activity or antigen, factor VIII coagulant activity, fibrinopeptides A and Bβ15-42, plasminogen, α-2-antiplasmin, functional and immunological tissue-plasminogen activator, thrombin-antithrombin complexes and D-dimer. Levels of tissue plasminogen activator inhibitor (activity and antigen) correlated with disease activity while fibrinogen and von Willebrand factor concentrations did not. Seven of the 18 subjects with Behçet's disease had suffered thrombotic events but it was not possible to distinguish these from the 11 patients without thrombosis using the assays performed. The results suggest the abnormal fibrinolytic activity in Behçet's disease is due to increased inhibition of tissue plasminogen activator. No abnormality of coagulation or fibrinolytic activity specific to Behçet's disease was detected.
