Three Types of Hereditary Antiterombin III Deficiency

The authors detected in the last seven years 15 patients with hereditary antithrombin III/AT III/ abnormality. All of them had typical clinical signs of recurrent arterious and venous thromboembolie. The abnormality inherited as an autosomal trait. Three types of the abnormality could be observed. In Type I both quantity and function of AT III were extremely decreased. In type II AT III is normal in quantity but abnormal in function. In Type III AT III is quantitatively normal and also its function seems normal as far as its basic activity is concerned /activity measured in absence of heparin/, but its abnormality becomes manifest in the presence of heparin in vitro/and also in vivo/. 5 of the patients belonged to Type I, 4 to Type II and 6 to Type III. In 60 examined family members of the 15 patients an abnormal AT III could be observed in 44, clinical signs in 23. The examination of AT III activity in the presence of a given amount of heparin ia of great importance in recognition of the different types of antithrombin III abnormalities.