[Homozygous antithrombin type HBS deficiency; a family study]

Congenital antithrombin (AT) deficiency is the most thrombotic genetic abnormality of haemostasis. Total quantitative deficits are lethal as early as life intra-uterine. Only homozygous mutations concerning the heparin-binding site are compatible with life. We report here the case of an 18 years old patient with recurrent deep venous thrombosis of the inferior members. Haemostasis exploration shows a decreased AT activity (11%) in the presence of heparin while AT progressive activity and AT antigen are normal. Two other homozygous sisters are identified in this family study. Molecular study of AT gene show Arg47-Cys substitution, already reported in the literature with patients of different geographic origins. Treatment of patients with homozygous AT type HBS deficiency is similar that for patients with heterozygous AT deficiency; a continuous prophylactic anticoagulant treatment is always necessary and AT concentrates infusions are required in all situations needing curative heparin treatment.