This post is also available in: English Slovenščina (Slovenian)

Inherited trombophilia, state that predisposes individuals to venous thrombosis may be due to deficiency of antithrombin III, deficiency of protein C or protein S, or resistance to acti­vated protein C. The impact of hereditary trombophilia in familial venous thrombosis is not completely understood. It is known that hereditary trombophilia by itself does not neces­sarily lead to development of venous thrombosis and that additional risk factors have to be present. In the present study hereditary thrombophilia was investigated in the families of patients with venous thrombosis and hereditary thrombophilia. Differences in biological fac­tors and differences in levels of hemostatic and hematological parameters between subjects with hereditary thrombophilia and venous thrombosis and assimptomatic carriers were stud­ied. Presence of the risk factor predisposing to venous thrombosis was also studied.

14 patients who had been diagnosed with venous thrombosis and inherited thrombophilia (8 females and 6 males, 25-50 years old, with a mean age of 41 years), and 34 close relatives of these patients (15 females and 19 males, 11-80 years old, with a mean age of 44 years), were included. In all subjects we measured the activity of antithrombin III, proteins C and S, and resistance to activated protein C, as well as activated partial thromboplastin time, throm­bin time, prothrombin time, fibrinogen, lupus anticoagulants, D-dimers, and complete blood cell count. Factors predisposing to venous thrombosis such as immobilisation of a limb, bed rest longer than three days, recent surgery, oral contraception, pregnancy and delivery were also assessed.

In 11 patients (79%) we detected resistance to activated protein C, and in the remaining 3 patients (21%) deficiency of antithrombin III was observed. Among the relatives of patients with resistance to activated protein C we found the same deficiency in 12 out of 23 sub­jects (52%). Three out of 11 (27%) relatives of patients with deficiency of antithrombin III had the same deficiency. Among relatives with resistance to activated protein C no one suf­fered venous thrombosis, while among relatives with antithrombin III deficiency one had venous thrombosis. In two relatives with venous thrombosis no hereditary thrombophilia could be detected. Among the relatives only three subjects suffered venous thrombosis in the past.

There were no significant differences in hemostatic and hematologic parameters among patients with venous thrombosis and asymptomatic subjects with inherited trombophilia. Subjects with inherited thrombophilia who had suffered venous thrombosis had been exposed to risk factors for thrombosis 3-times more often than subjects with inherited trom- bophilia who had remained symptom-free.

Results of this study show that resistance to activated protein C is the most common form of inherited thrombophilia. This defect was found in about one half of close relatives of patients with venous thrombosis and resistance to activated protein C. It was concluded that inher­ited thrombophilia does not necessary lead to symptomatic venoue thrombosis unless other risk factors are present.