Thrombotic events in severe FXII deficiency in comparison with unaffected family members during a long observation period.

To investigate the occurrence of thrombotic events (myocardial infarction, deep vein thrombosis or ischemic stroke) in a group of 39 cases of severe FXII deficiency during a mean 22.5 years follow-up. All patients seen in Padua during the years 1968-2006 will the object of this investigation. FXII was less than or 1% of normal in all cases. Factor FXII activity in unaffected family members was 98% (range 90-140%). No patient or control had a thrombotic event in the past and none were on anticoagulant therapy. FV Leiden was present in one patient and in two controls whereas the G to A20210 prothrombin polymorphism was absent in both groups. There was one death among the patients (breast cancer) and one among the control (car accident). There were two thrombotic events (myocardial infarction and deep vein thrombosis) in the patient group and three (myocardial infarction and two deep vein thrombosis) in the control group. Heterozygous FV Leiden was present in the patient who had venous thrombosis, One of the two control subjects who developed venous thrombosis had heterozygous FV Leiden and was on oral contraception. The second control subject who developed venous thrombosis was on oral contraception and had varicose veins. No ischemic stroke was observed in the patients or controls. Periods of immobilization were 42 days and 38 days, respectively for FXII deficient patients and for the controls. Patients with severe FXII deficiency may present thrombotic events but these are similar to these presented by unaffected family members. As a consequence it may be stated that severe FXII deficiency does not appear to effect thrombotic events.