AbstractThe antiphospholipid antibody syndrome (APS) is defined by the persistent presence of antiphospholipid antibodies in patients with recurrent venous or arterial thromboembolism or pregnancy morbidity. Anti-thrombotic therapy is the mainstay of treatment given the high risk of recurrent thromboembolism that characterizes this condition. Despite the prothrombotic nature of APS, thrombocytopenia is present in a proportion of patients. which can complicate management and limit the use of antithrombotic therapy. The mechanism of APS-associated thrombocytopenia is multifactorial and its relation to thrombotic risk poorly characterized. However, the presence of thrombocytopenia does not appear to reduce thrombotic risk in patients with APS, who can develop thromboembolic complications necessitating antithrombotic treatment. In these cases, treatment of the thrombocytopenia may be necessary to facilitate administration of antithrombotic agents. Clinical trials have demonstrated that patients with antiphospholipid antibodies and venous thromboembolism should be treated with vitamin K antagonists (warfarin); that ischemic stroke may be treated with aspirin or warfarin; and that women with recurrent pregnancy loss should receive prophylactic-dose heparin and aspirin. However, application of these trial results to patients with APS-associated thrombocytopenia can be challenging since there are limited data on the optimal use of antithrombotic agents in this setting. Issues such as determining the platelet threshold at which antithrombotic agents can be safely used and managing patients with both bleeding and thromboembolic complications remain unresolved. Ultimately the risks and benefits of antithrombotic therapy, balanced against the severity of the thrombocytopenia and its potential bleeding risks, need to be assessed using an individualized patient approach.
