A 45-year-old man with antiphospholipid syndrome has recurrent venous thrombosis. Laboratory shows prolonged aPTT that does not correct with normal plasma, positive lupus anticoagulant by dilute Russell viper venom time, and normal PT. Which antiphospholipid antibody is most strongly associated with thrombosis?
- A Anti-β2 glycoprotein I IgG ✓
- B Anti-cardiolipin IgM
- C Anti-prothrombin antibody
- D Anti-annexin V antibody
Correct answer: A. Anti-β2 glycoprotein I IgG
Explanation
Anti-β2 glycoprotein I (β2GPI) IgG is the antiphospholipid antibody most strongly associated with clinical thrombosis. β2GPI binds anionic phospholipids on endothelial cells, platelets, and monocytes; anti-β2GPI antibodies disrupt anticoagulant mechanisms and activate endothelium. Triple positivity (lupus anticoagulant, anti-cardiolipin, anti-β2GPI) carries the highest thrombotic risk. The prolonged aPTT in vitro is paradoxical because the syndrome causes thrombosis in vivo.
Reference: Harrison's Principles of Internal Medicine, 20th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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