A 30-year-old woman with SLE develops thrombocytopenia and the laboratory shows prolonged aPTT that does NOT correct on 1:1 mixing with normal plasma, anti-β2-glycoprotein I antibodies, and lupus anticoagulant. The most likely haematological complication she is at risk for is:

• A Haemophilia-like bleeding from factor inhibitor
• B Arterial and venous thrombosis ✓
• C DIC with microangiopathic haemolysis
• D Selective platelet dysfunction without thrombosis risk

Explanation

Antiphospholipid antibody syndrome (APLAS) is paradoxically associated with thrombosis (both arterial and venous) and pregnancy morbidity despite the in vitro finding of a prolonged aPTT (due to lupus anticoagulant inhibiting phospholipid-dependent clotting reactions). The failure to correct on 1:1 mixing confirms an inhibitor rather than factor deficiency. Anti-β2-GPI and anticardiolipin antibodies are the culprits. Thrombocytopenia in APLAS is caused by platelet-antibody binding and platelet consumption, not a coagulation factor defect.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.