先天性アンチトロンビンＩＩＩ欠乏症

Antithrombin III (AT III) is not only a most potent thrombin inhibitor but also an inhibitor against coagulation factors Xa, XIa, IXa, and XIIa and heparin accelerates the inhibitory reaction of AT III remarkably. Since Egeberg first described an inherited AT III deficient family, about thirty articles dealing with inherited AT III deficient families have been published as full papers. The present review analyzes the relation between AT III deficiency and thrombotic tendency in the inherited AT deficient families.<br>The mean age of the propositus was 30.2±14.2y/o (mean±S. D.) and the sex distribution was male dominant (male: female ratio approximately 2:1). The cases where the propositus had been suffering from recurrent thrombosis was 36%, and that of the first episode of thrombosis for the propositus was 48%. The sites of thrombosis were located mostly in the veins of the lower half of the body such as the ilio-femoral vein, the deep veins of the legs, mesenteric vein and vena cava inferior, often complicating with pulmonary embolism.<br>The total numbers of persons in the inherited AT III deficient families whose AT III was examined, amounted to 434 in 23 articles. Depressed AT III level measured by either the immunological or biological method was found in 189 persons. The average appearance rate of AT III deficient persons in the affected families was 52.1±18.0%. The incidence of persons who had both AT III deficiency and thrombotic episodes was calculated by dividing the numbers of AT III deficient persons by the total number of persons whose AT III was examined in the deficient family. The average value for the affected families was 26.5±12.8%.<br>These figures thus indicate that about half of the persons in the inherited AT III deficient families had AT III deficiency, and that about half of these AT III deficient persons had thrombotic episodes. Analysis of the reports on the inherited AT III deficiency thus revealed that AT III deficiency did not always induce thrombosis: in younger age group, thrombosis was never apparent. Additional factors which induce thrombosis in AT III deficient persons must therefore be present. Trauma, surgery, or pregnancy may be one of such factors. About one quarter of the persons in the affected families had AT III deficiency without thrombosis. The existence of such “silent” AT III deficiency suggests that the incidence of inherited AT III deficiency may be much higher than anticipated.