lupus anticoagulant

Etiology

• lupus erythematosus (30%) & other autoimmune disorders
• infections
  • bacterial infection
  • viral infection, especially HIV
  • protozoal infection
• pharmacologic agents
  • chlorpromazine (Thorazine)
  • procainamide
  • hydralazine
  • antibiotics
  • cocaine
  • Dilantin
  • quinidine
  • quinine
• lymphoproliferative disorders
  • Waldenstrom's macroglobulinemia
  • lymphoma
  • hairy cell leukemia

Epidemiology

found in 2% of normal individuals

Pathology

• antiphospholipid antibody
  • antibodies to cardiolipin may be present
• prolonged PTT (in vitro phenomenon)
• confers hypercoagulable state in vivo
  • predisposes to arterial & venous thrombosis
  • possible mechanisms
    • interference with anticoagulant activity of protein C
    • activation of platelets
    • inhibition of PGI2 production by endothelial cells

Laboratory

• lupus anticoagulant may be suspected when a prolonged PTT is not correcting by mixing the patient's plasma 50:50 with control plasma (indicating an inhibitor of in vitro anticoagulation)
• lupus anticoagulant in plasma is confirmed by:
  • comparing the PTT of the patient's plasma to control plasma in the presence of a dilute solution of phospholipids
  • dilute Russell's viper venom clotting time
• abnormal aPTT is corrected by substituting activated or resting platelets for exogenous phospholipid
• hexagonal phospholipid neutralization test is useful when the patient is anticoagulated with heparin or warfarin

Management

see antiphospholipid syndrome

More general terms

• autoantibody

Additional terms

• anticoagulant
• antiphospholipid syndrome (APS); Hughes syndrome
• hexagonal phospholipid neutralization test

Patient information

lupus anticoagulant patient information