A survey of inherited thrombotic syndromes in Italy. ad hoc Study Group.

A collaborative survey was conducted among Italian thrombosis centers to gather information about the number and clinical features of patients with inherited thrombotic syndromes. The survey, based on 74 unrelated kindreds, revealed that antithrombin III, protein C and protein S defects are the most frequent genetic disorders. Venous thromboembolism was more frequent than arterial thrombosis, which was seen in only a minority of cases, most frequently with dysfibrinogenemia. About half of the patients developed venous thrombosis with a similar incidence in antithrombin III, protein S and protein C defects. About half of the symptomatic patients had recurrences and 40% developed thrombosis after a triggering factor, most frequently after surgery, during the puerperium, pregnancy, oral contraceptive intake or bed rest. Deep venous thrombosis prevailed and superficial thrombophlebitis was rare in antithrombin III-deficient patients, whereas deep venous thrombosis was present in about half and superficial thrombophlebitis in about one third of the cases with protein S and protein C defects. The probability to be free of thrombosis decreases with increasing age and at 35 years can be estimated to be 47% both for men and women. There is, however, a group of patients who are still free of thrombosis despite their older ages.