Antiphospholipid syndrome, a recurrent state of venous or arterial thrombosis, is associated with antibodies directed against membrane anionic phospholipids (i.e., anticardiolipin [aCL] antibody, antiphosphatidylserine) or corresponding plasma proteins, predominantly beta-2 glycoprotein I (apolipoprotein H). This evidence concerns the gene APOH and antiphospholipid syndrome.