الفهرس 
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Abstract
Antiphospholipid syndrome (APS) is an autoimmune disease of unknown cause that manifests clinically as recurrent venous or arterial thrombosis and/or pregnancy morbidity. Characteristic laboratory abnormalities in APS include persistently elevated levels of antibodies directed against membrane anionic phospholipids as (anticardiolipin antibody [aCL] and antiphosphatidylserine) or their associated plasma proteins, predominantly beta-2 glycoprotein I (apolipoprotein H) or evidence of a circulating anticoagulant (lupus anticoagulant).
Antiphospholipid antibodies (APAs) are a heterogeneous group of autoantibodies that are not directed against phospholipids alone, but against a wide variety of phospholipid binding proteins (B2GPI, prothrombin, protein C, protein S, annexin V, thrombomodulin, factor XII and others). B2GPI is the most important antigenic target of APAs. APAs are found in 1-5% of healthy population and they may be present in autoimmune diseases other than APS.
Antiphospholipid syndrome and antiphospholipid antibodies can occur either alone or in association with systemic autoimmune diseases, most commonly systemic lupus erythematosus (SLE). Approximately half the patients with APS have no underlying systemic autoimmune diseases.
Antiphospholipid syndrome is more common in young to middle aged adults with female predominance (80%). There is association between anticardiolipin antibody and groups of individuals who carry certain HLA genes, including DRW53, DR7 and DR4.
The aPL antibodies have been implicated in reactions that interfere with almost all known hemostatic and endothelial cell reactions through inhibition of protein C and protein S cofactor activity, induction of tissue factor in endothelial cells and monocytes, inhibition of tissue factor pathway inhibitor and tissue-type plasminogen activator (tPA) activity, inhibition of fibrinolysis via interaction with antiplasmin, induction of platelet aggregation, induction of microparticle formation and endothelial cell adhesion receptors. Some evidence regarding the effect of aPL antibodies on the complement has been described recently, and related to pregnancy complications and thrombosis.
Thrombosis of the deep limb vein with or without pulmonary embolism is the most frequently reported manifestation in this syndrome and ischaemic stroke is the most common arterial thrombotic manifestation. Antiphospholipid antibodies were found in 4 to 21% of patients presenting with venous thromboembolism and they were found in 18% of young patients with stroke. APS account for about 15% of cases of fetal loss.
APS is a heterogenous disorder in term of clinical manifestations as more than one pathophysiological process may play a role in its development. Sydney criteria are currently the basis for diagnosis of APS. The inclusion of antibodies against 2GPI in the new criteria as a sufficient laboratory test for diagnosis of definite APS is a major change. New treatment modalities have been proposed as a possible alternatives to the current treatment options such agents that target receptor molecules, postreceptor mediators and effector proteins. HSCT may give a hope for patients with refractory APS.
Aim of the Work: Updated overview of various aspects of the antiphospholipid syndrome.