Antiphospholipid antibodies and antithrombin deficiency: double trouble for pregnancy

Exploring antithrombin: insights into its physiological features, clinical implications and analytical techniques

Antithrombin is an essential protein that acts as a natural anticoagulant in the human body. It is synthesized by the liver and belongs to the serine protease inhibitors, which are commonly referred to as the SERPINS superfamily. The antithrombin molecule comprises 432 amino acids and has a molecular weight of approximately 58 200 D. It consists of three domains, including an amino-terminal domain, a carbohydrate-rich domain, and a carboxyl-terminal domain. The amino-terminal domain binds with heparin, whereas the carboxyl-terminal domain binds with serine protease. Antithrombin is a crucial natural anticoagulant that contributes approximately 60-80% of plasma anticoagulant activities in the human body. Moreover, antithrombin has anti-inflammatory effects that can be divided into coagulation-dependent and coagulation-independent effects. Furthermore, it exhibits antitumor activity and possesses a broad range of antiviral properties. Inherited type I antithrombin deficiency is a quantitative disorder that is characterized by low antithrombin activity due to low plasma levels. On the other hand, inherited type II antithrombin deficiency is a qualitative disorder that is characterized by defects in the antithrombin molecule. Acquired antithrombin deficiencies are more common than hereditary deficiencies and are associated with various clinical conditions due to reduced synthesis, increased loss, or enhanced consumption. The purpose of this review was to provide an update on the structure, functions, clinical implications, and methods of detection of antithrombin.

Recurrent thrombosis prevention with intravenous immunoglobulin and hydroxychloroquine during pregnancy in a patient with history of catastrophic antiphospholipid syndrome and pregnancy loss

We report a case of a 36-year old patient with prior history of thrombosis in a setting of antiphospholipid antibody syndrome (APS) as well as pregnancy-associated catastrophic antiphospholipid syndrome (CAPS), resulting in multi-organ infarction and pregnancy loss. The episode of CAPS occurred while she was receiving antepartum low-dose aspirin and therapeutic-dose enoxaparin. This patient presented again at 6 weeks gestation and ultrasounds were consistent with fetal growth restriction, concerning for placental insufficiency and thrombosis. This time, hydroxychloroquine and monthly intravenous immunoglobulin (IVIG) infusions were added to her prophylaxis regimen, resulting in a successful delivery. Platelet count and antiphospholipid antibody titers were routinely monitored throughout pregnancy as markers of disease activity for APS. Current thromboprophylaxis guidelines do not address therapeutic options to prevent further pregnancy morbidity in women who develop recurrent episodes of thrombosis or CAPS despite receiving adequate anti-thrombotic treatment. Use of hydroxychloroquine and IVIG has been associated with good outcomes in this subset of patients.

Clinical syndromes associated with acquired antithrombin deficiency via microvascular leakage and the related risk of thrombosis

Antithrombin (AT) is a 65kDa glycoprotein belonging to a group of inhibitory factors known as serpins (serine protease inhibitors). It plays a critical role in the inhibition of coagulation and inflammation processes within the environment of the vascular endothelium. Inadequate levels of functional AT in plasma results in an increased risk of thrombotic events, both venous and arterial. AT deficiency can be inherited or acquired. Congenital AT deficiency is the most severe inherited thrombophilic condition with an odds ratio of 20 for the increased risk of venous thrombosis. Acquired AT deficiency occurs in a variety of physiologic and pathologic medical conditions with similar risks of increased thrombosis. In this article, we review clinical settings characterized by an acquired AT deficiency largely or partly subsequent to protein microvascular leakage. Other different mechanisms of AT depletion are implied in some clinical conditions together with endothelial loss, and, therefore, outlined. In addition, we provide a description of the current knowledge on the specific mechanisms underlying endothelial AT leakage and on the consequences of this protein decrease, specifically looking at thrombosis. We identify potential directions of research that might prove useful in patients with acquired AT deficiency.