We have studied the fibrinolytic system in one asymptomatic and six symptomatic members of a family with recurrent DVTs in three generations. Tissue plasminogen activator activity (TPA) and fast acting inhibitor of TPA (PAI) were determined using chromogenic substrate and TPA antigen with ELISA. Measurements were made at rest and after 10 and 20 minutes of venous occlusion (VO). 17 healthy subjects served as controls. The mean TPA in the seven family members was significantly lower than in controls at 10 and 20 min VO (p< 0.01).TPA was below the lowest value of controls (<1.7 U/ml) in five of the six patients with DVT at 10 min VO and remained below the range of controls in three at 20 min VO (<3.3 U/ml). The lowered TPA activity was associated with impaired release of TPA antigen (mean level at 10 min VO 12.A ng/ml, controls 19.5 ng/ml, p<0.05; at 20 min VO 18.2 ng/ml, controls 43.2 ng/ml, p<0.01). Four .patients with and one without DVT had TPA antigen below the lowest level of controls at 10 and/or 20 min VO. The level of'PAI at rest was normal in all cases (from 0.6 to 1.7 U/ml, controls from 0 to 3.7 U/ml). In accordance with low release of TPA antigen PAI was consumed less during VO in patients than in controls (mean level at 20 min VO 0.9 U/ml, controls 0.4 U/ml, p<0.05). The levels of antithrombin III, protein C, protein S, plasminogen, fibrinogen, F V, F VIII:C, vWf:Ag, fibrinopeptide A and beta-thromboglobulin were normal . Circulating anticoagulant was not found. It is concluded that impaired release of TPA, independent of PAI, is associated with DVT in this family. The pattern of inheritance suggested autosomal dominant trait.
Elevation of Blood Plasminogen Activator Inhibitor Level in Patients With Cerebral Venous Thrombosis
