Antifactor Xa Activity in Thrombophilia Studies in a Family with At-III Deficiency

Abstract

Antithrombin III (At-III) concentration and amidolytic assays reflecting functions of the At-III molecule were studied in members of a family with a strong tendency to thrombosis. Antifactor Xa and heparin cofactor activity closely paralleled the At-III concentration. In all individuals with a history of thrombosis At-III concentration was about 50% of normal. The clinical features and causes of death are briefly reviewed. Mean age in deceased family members with a tendency to thrombosis was 55 years, in members with no history of thrombosis it was 65 years.