[Abnormal antithrombin III: abnormalities of heparin or protease binding domain]

Two patients with abnormal antithrombin III manifested abnormality in heparin binding activity (abnormal antithrombin III "Toyma") or protease binding activity (abnormal antithrombin III "Aomori"). Antithrombin III "Toyama" is hereditarily homozygous with Arg47 to Cys47 (TGC-->TGT) mutation, and antithrombin III "Aomori" is hereditarily heterozygous with Arg393 to His393 (CGT-->CAT). The former is classified as type II-c, and the latter as type II-b according to Lane's classification2). Both patients showed cerebral thrombosis after age 20. Heparin cofactor II activity in the former case was slightly higher than normal. Oral anticoagulant therapy was used in the both cases. These cases were examined by biological and immunological assay, heparin sepharose column chromatography, binding activity to cultured porcine endothelial cells, restriction fragment length polymorphysm and polymerase chain reaction. The authors developed an antithrombin III assay method to be able to estimate real activity without the influence of heparin cofactor II activity11), and to apply the low molecular weight heparin to prevent relapse of thrombosis, and finally to find an anticoagulant substance in an interesting case of hepatocellular carcinoma (Edmondson type 1) producing normal antithrombin III30).