anticardiolipin

Anticardiolipin antibodies are autoantibodies directed against cardiolipin, a phospholipid that is a component of cell membranes, especially when bound to the protein beta2-glycoprotein I. The antibodies are predominantly of the IgG and IgM isotypes, though IgA can be present. They are usually detected by enzyme-linked immunosorbent assays (ELISA) and are reported as IgG or IgM titers; higher titers may carry greater clinical significance in some contexts.

Clinically, anticardiolipol antibodies are a major laboratory criterion for antiphospholipid syndrome (APS), which can occur as a primary condition or in association with autoimmune diseases such as systemic lupus erythematosus. The presence of anticardiolipin antibodies is associated with an increased risk of arterial or venous thrombosis and adverse pregnancy outcomes, including recurrent miscarriage, placental insufficiency, and preterm birth. However, aCL positivity alone does not confirm APS; the diagnosis requires both clinical events and laboratory criteria, with antibodies detected on two occasions at least 12 weeks apart.

Pathophysiology is not fully understood but is thought to involve antibodies against cardiolipin–beta2-glycoprotein I complexes that promote thrombosis by activating endothelial cells and platelets, modulating coagulation pathways, and disrupting the annexin A5 anticoagulant shield. In vitro coagulation tests such as the aPTT may be prolonged, even though there is a prothrombotic tendency in vivo.

Management depends on clinical history. Thrombosis typically warrants long-term anticoagulation, often with warfarin aiming for an INR of 2.0–3.0. In obstetric APS, treatment may include low-dose aspirin plus heparin during pregnancy. Individuals without thrombosis and who do not meet diagnostic criteria usually do not require chronic anticoagulation; risk reduction includes avoiding estrogen-containing contraceptives and managing underlying conditions.