Lupus anticoagulants (or antiphospholipid antibodies) are specific antibodies with affinity for anionic phospholipids. The most common targets are beta2-glycoprotein I, prothrombin, protein C and protein S. In human patients, lupus anticoagulants or antiphospholipid antibodies occur in patients with SLE, other immune-mediated diseases, drug-induced disorders and certain infectious diseases. The syndrome is associated with arterial and venous thrombosis, recurrent fetal loss and thrombocytopenia. The exact mechanism how these antibodies induce thrombosis is not known, and mechanisms may differ depending on the antibody specificity.
Antiphospholipid antibodies were detected in a 2 year-old Chesapeake Bay Retriever with hemolytic anemia, nephrotic syndrome, polyarthropathy, thrombocytopenia and pulmonary thromboembolism. The dog had a normal PT, negative FDPs, a high fibrinogen, a mildly prolonged ACT, and a persistently long APTT which did not correct when mixed with normal dog plasma in vitro or after prolonged incubation. The dog also had a prolonged Russell viper venom time (RVVT) and kaolin clot time (KCT), confirming the presence of the antibodies, because assays sensitive to deficiencies in phospholipid (APTT, RVVT, KCT) will be prolonged in animals with antiphospholipid antibodies.
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