Article

Inherited antithrombin deficiency: A review

Department of Internal Medicine, University of Minnesota School of Medicine, Minneapolis, MN, USA.
Haemophilia (Impact Factor: 2.6). 12/2008; 14(6):1229-39. DOI: 10.1111/j.1365-2516.2008.01830.x
Source: PubMed

ABSTRACT

Antithrombin (AT) is a potent inactivator of thrombin and factor Xa and the major inhibitor of blood coagulation. Inherited AT deficiencies are uncommon, with prevalences in the general population between 1 in 500 and 1 in 5000. They are either quantitative (type I) or qualitative (type II). Type II is subdivided into the more common, but less thrombogenic, type IIb deficiency caused by a defect in the heparin-binding region of AT and the less common, but more thrombophilic, type IIa variant caused by mutations in the thrombin-binding site. A pleiotropic type IIc deficiency also exists. In the evaluation of a thrombophilic individual, a functional AT assay (AT activity) should be used and the diagnosis of AT deficiency only established after acquired causes have been ruled out and repeat AT testing on an additional sample has been performed. A subsequent antigenic AT assay result leads to differentiation between type I and type II deficiency. Further specialized tests help subclassify the type II deficiencies, but this is typically not carried out for clinical purposes, even though it might be helpful to assess thrombosis risk. AT deficiency is associated with an increased risk for venous thromboembolism (VTE) and pregnancy loss. The association with arterial thrombosis is only weak. VTE prophylaxis and treatment management will be discussed in this article and existing treatment guidelines presented. The lack of data surrounding the use of AT concentrates and the resulting ambiguity as to when to use such concentrates will be discussed.

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    • "The human gene encoding AT (SERPINC1) is located on the chromosome 1q23-25 and consists of 7 exons and 6 introns [1] [2]. Currently, over 300 mutations causing AT deficiency have been reported [3]. "
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    ABSTRACT: Antithrombin (AT) deficiency is a rare autosomal dominant disorder which increases the risk of venous thromboembolism (VTE). We report here the case of type II antithrombin deficiency in 44-year-old man who developed left leg deep vein thrombosis (DVT). All exons of SERPINC1, the gene encoding AT were amplified by PCR followed by direct sequencing. A heterozygous mutation c.166C>T in exon 2 causing the amino acid substitution of Arg to Cys at residue 56, was found. This mutation does not affect the folding and secretion of the protein, but impairs the heparin affinity, reducing the anticoagulant activity of AT.
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    • "The prevalence of this mutation in Europe is about 2–3% for heterozygous carriers and VTE risk is increased 2–4 fold [10]. On the other hand, deficiency of naturally existing anticoagulants like antithrombin, protein C or protein S can be caused by heritable genetic defects [11] [12]. Heritable thrombophilia is also discussed for patients with klinefelter syndrome and chronic leg ulcers. "
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    • "The leading causes of inherited thrombophilia in Caucasians are the activated protein C resistance -in most cases due to the Factor V Leiden polymorphism -and the prothrombin G20210A gene polymorphism [3,4]. Besides these two common thrombophilic conditions (prevalence in the general population of 3-7% and 0.7-4%, respectively) [2], reductions in plasma natural anticoagulants (antithrombin [AT], protein C [PC] or protein S [PS]) have long been recognized as rare, but potent risk factors for VTE [5] [6] [7]. "
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    ABSTRACT: Natural anticoagulants deficiency (antithrombin [AT], protein C [PC], protein S [PS]) is a rare, but potent risk factor for venous thromboembolism (VTE). We performed a meta-analysis of observational studies evaluating the impact of inherited natural anticoagulants deficiency on VTE risk. Case-control and cohort studies evaluating the association of these abnormalities with VTE were systematically searched in the PubMed, Web of Science, Scopus and EMBASE databases. Twenty-one studies were included in the analysis. Thirteen studies (3,452 cases and 11,562 controls) showed an increased risk of first VTE in AT deficient subjects compared to controls (OR: 16.26, 95%CI:9.90-26.70; P<0.00001). An increased risk of first VTE was also found in PC (11 studies, 2,554 cases and 9,355 controls; OR: 7.51, 95%CI:3.21-17.52; P<0.00001) and PS deficient patients (14 studies, 4,955 cases and 9,267 controls; OR: 5.37; 95%CI:2.70-10.67; P<0.00001) compared to controls. Evaluating the risk of VTE recurrence, we found a significant association with AT (4 studies, 142 cases and 1,927 controls; OR: 3.61; 95%CI:1.46-8.95; P=0.006) and with PC (2 studies, 80 cases and 546 controls; OR: 2.94; 95%CI:1.43-6.04; P=0.03), but not with PS deficiency (2 studies, 57 cases and 589 controls; OR: 2.52; 95%CI:0.89-7.16; P=0.08). Sensitivity and subgroup analyses confirmed these results. The association among natural anticoagulants deficiency and VTE was maximal for patients with unprovoked events. The VTE risk is increased in patients with natural anticoagulants deficiency, but additional studies are warranted to better assess the risk of VTE recurrence. Copyright © 2015. Published by Elsevier Ltd.
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