As the name implies, coagulation inhibitors (circulating anticoagulants) interfere with normal blood coagulation. Coagulation inhibitors may be congenital or acquired (developing in patients during a disease) and are almost always immunoglobulins, either IgG, IgM, or IgA. Two types of inhibitors are directed toward a coagulation factor (or multiple factors) and the lupus anticoagulant.
Lupus anticoagulant is one of the more commonly encountered coagulation inhibitors. It is also known as an antiphospholipid antibody because it is directed toward phospholipids. Antiphospholipid antibodies bind a variety of protein-phospholipid complexes and, because of this, are sometimes referred to as nonspecific inhibitors. Lupus anticoagulant is usually an IgG antibody. It differs from factor-specific inhibitors because lupus anticoagulant causes thrombosis and abnormal clotting, while factor-specific inhibitors cause severe bleeding.
