Antiphospholipid antibodies

Antiphospholipid syndrome (APS)

• ✓ if: SLE, age <40 y & arterial thromb, recurrent venous thromb, spontaneous abortion

• ACL: Ab against cardiolipin, a mitochondrial phospholipid; IgG more specific than IgM

• LA: Ab that prolongs phospholipid-dependent coagulation reactions; ∴ ↑ PTT that does not correct with mixing study but does correct with excess phospholipids or platelets; PT not affected b/c the reaction contains much more phospholipid

• β2-GP-I: Ab against β2-glycoprotein-I, IgG or IgM (uncertain role of Abs in pathogenesis)

• False ⊕ VDRL nontreponemal test for syphilis (cardiolipin is part of Ag complex)

• Risk of thromboembolic phenomena may increase with titer of APLs