## Antiphospholipid Syndrome — Clinical Features and Management ### Correct Answer Analysis **Hydroxychloroquine is NOT first-line anticoagulation for APS.** Hydroxychloroquine is an adjunctive immunomodulatory agent used in SLE-associated APS, but the primary anticoagulant is **warfarin** (target INR 2–3) or **DOAC** (in selected cases). Hydroxychloroquine may reduce thrombotic recurrence when added to anticoagulation, but it is never monotherapy for APS thrombosis. ### Why the Other Options Are Correct | Feature | Details | |---------|----------| | **Lupus anticoagulant paradox** | Prolongs aPTT in vitro (phospholipid-dependent test) but causes thrombosis in vivo by activating endothelium and platelets | | **Anticardiolipin antibodies** | Most specific antibody marker; IgG > IgM in clinical significance; part of Sydney diagnostic criteria | | **Thrombosis > bleeding** | APS is a hypercoagulable state; bleeding is rare unless anticoagulation is excessive or concurrent DIC | ### Management of APS-Related Thrombosis **Key Point:** First-line anticoagulation is **warfarin** (INR 2–3) or **DOAC** (apixaban, rivaroxaban emerging evidence). Hydroxychloroquine is added as adjunctive therapy in SLE-APS to reduce recurrence risk, not as primary anticoagulant. **Clinical Pearl:** The "paradox" of lupus anticoagulant — it causes in vitro anticoagulation (prolonged aPTT) but in vivo thrombosis — is a classic NEET PG trap. Remember: anticoagulant in the test tube, but procoagulant in the patient. **High-Yield:** APS diagnostic criteria require **both** clinical (thrombosis or pregnancy morbidity) AND laboratory criteria (LA, aCL, or anti-β2-GPI) on ≥2 occasions ≥12 weeks apart. [cite:Harrison 21e Ch 179]
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