Like many autoimmune diseases, it is more common in women than in men. APS is more common in young to middle-aged adults; however, it also manifests in children and elderly people. The actual frequency of APS in the general population is unknown. One to 5% of healthy individuals have aPL antibodies. aPL antibodies are found in approximately 30-40% of patients with SLE, but only about 10% have APS. Approximately half of APS cases are not associated with another rheumatic disease.
The exact cause is not known, but activation of the system of coagulation is evident. There are three primary classes of antibodies associated with APS, including anti-cardiolipin antibodies, the lupus anticoagulant and antibodies directed against beta-2-glycoprotein 1.
The most common clinical manifestation of antiphospholipid syndromeis thrombosis, which can affect the vessels of any organ. Damage depends on the extent and location of the clot. There are three distinct APS disease entities: primary (the absence of any comorbidity), secondary (when there is a pre-existing autoimmune condition, most frequently systemic lupus erythematosus, SLE), and catastrophic (when there is simultaneous multi-organ failure with small vessel occlusion). Catastrophic APS (CAPS) is often a fatal manifestation with a mortality rate of approximately 50%.
