HOMOZYGOUS ANTITHROMBIN DEFICIENCY - REPORT OF 2 NEW CASES (99-LEU TOPHE) ASSOCIATED WITH ARTERIAL AND VENOUS THROMBOSIS

Inherited antithrombin deficiency is associated with an increased risk of thrombosis, primarily venous rather than arterial. Most affected i ndividuals have inherited only a single copy of an abnormal antithromb in (AT) gene. Homozygously affected individuals, although rare, have a severe thrombotic history of early onset and often affecting the arte ries. We report two new cases of type II HBS (heparin binding site) de ficiency in which the propositi are homozygous for the previously repo rted mutation 99 Leu to Phe, and who have a severe thrombotic history. These cases are considered alongside existing homozygote and compound heterozygote cases.