The designation 'antiphospholipid syndrome' was proposed for the association of arterial and venous thrombosis, recurrent fetal loss, and immune thrombocytopenia with a spectrum of autoantibodies directed against cellular phospholipid components. Anticardiolipin antibodies may react with cardiolipin and with other negatively charged phospholipids, including beta-2-glycoprotein I (B2GPI, APOH; 138700). The term 'lupus anticoagulant' refers to a heterogeneous group of antibodies, most commonly of the IgG type, that are detected by their inhibitory effect on coagulant-active phospholipid components of in vitro coagulation tests (summary by Matthey et al., 1989). Shoenfeld et al. (2008) noted that antiphospholipid syndrome is characterized by up to 30 different autoantibodies, including those against platelets, glycoproteins, coagulation factors, lamins, mitochondrial antigens, and cell surface markers. Some of these may have an additive effect on the prothrombotic tendency of the syndrome. Ruiz-Irastorza et al. (2010) reviewed pathophysiologic, clinical, diagnostic, and therapeutic advances related to the antiphospholipid syndrome. Various autoimmune disorders that cluster in families, including autoimmune thrombocytopenia (188030), are discussed elsewhere (e.g., 109100, 269200).