[Antithrombin homozygous type II HBS deficiency (99Leu-Phe) associated with recurrent arterial thrombosis]

Antithrombin (AT) is a natural anticoagulant and serine protease inhibitor. Hereditary AT deficiencies are uncommon and are associated with a higher risk of venous thrombo-embolism (VTE) compared to other thrombophilias. They are either quantitative (type I) or qualitative (type II) and various mutations have been reported. The II HBS deficiency is caused by a defect in the heparin-binding region (HBS) of AT. This homozygous deficiency increases the risk of VTE. The association with arterial thrombosis is weak but a few cases have been reported. We report a 20-year-old female with recurring arterial thrombosis associated with an AT type II HBS deficiency, due to a homozygous mutation Leu99Phe. In young patients, with recurrent and unexplained arterial thrombosis, a biologic thrombophilia has to be comprehensively searched.