Antiphospholipid syndrome (APS), also known as antiphospholipid antibody syndrome, is associated with a tendency to abnormal blood clotting and other features. Problems in patients with APS can include clots in either veins or arteries, skin changes, low platelet counts, heart valve abnormalities and the risk of pregnancy loss. APS can occur in combination with another disease, most commonly systemic lupus erytematosus, or can occur with no associated condition. APS diagnosis requires at least two positive blood tests (lupus anticoagulant, anticardiolipin antibody or anti-ß2 glycoprotein 1) spaced at least 3 months apart, since antibodies that suggest this condition can occur for brief periods in patients without APS. Patients with APS who develop clots generally require long-term blood thinning.