A 30-year-old woman with SLE has recurrent arterial thromboses and elevated anti-phospholipid antibodies. These antibodies cause thrombosis primarily by:

• A Inhibiting protein C activation and activating endothelial cells and platelets ✓
• B Activating factor XII via the contact activation pathway
• C Cross-reacting with fibrin monomers and preventing fibrinolysis
• D Causing complement-mediated lysis of endothelial cells

Explanation

Antiphospholipid antibodies (anti-cardiolipin, lupus anticoagulant, anti-beta2-glycoprotein I) promote a prothrombotic state by inhibiting anticoagulant pathways (protein C, annexin V), activating endothelial cells to upregulate tissue factor and adhesion molecules, and activating platelets. This results in recurrent arterial and venous thromboses and recurrent pregnancy loss (antiphospholipid syndrome, APS).

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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