Lupus Anticoagulant

Key Features

• Lupus anticoagulants prolong activated partial thromboplastin time (aPTT) by interfering with interactions between the clotting cascade and the phospholipid surface on which they function

• Predispose to thrombosis rather than to bleeding

• Antibodies may also interfere with factor II activity (rare); this tiny subset of patients are at risk for bleeding

• They were so named because of their early identification in patients with systemic lupus and other connective tissue diseases

• May occur with increased frequency in individuals with underlying infection, inflammation, or malignancy

• Can occur in asymptomatic individuals in the general population

Clinical Findings

• No bleeding

• Increased risk of thrombosis and recurrent spontaneous abortions

Diagnosis

• Prolonged aPTT that does not correct completely on mixing but that normalizes with excessive phospholipid

• Specialized testing can confirm presence of lupus anticoagulant

  • Positive hexagonal phase phospholipid neutralization assay

  • Prolonged dilute Russell viper venom time

  • Positive platelet neutralization assays

Treatment

• No specific treatment necessary

• Anticoagulation in standard doses for patients with thromboses, aiming for INR of 2.0–3.0

• Because of artificially prolonged PTT, unfractionated heparin therapy is difficult to monitor; thus, weight-based low-molecular-weight heparin is preferred

• Prophylaxis during pregnancy should be with low-molecular-weight heparin