skip to main content

Antiphospholipid Syndrome — SCE Rheumatology MCQ

Instant feedback + full explanation. One question, done properly.

HardAutoimmune SerologyAntiphospholipid SyndromeSCE Rheumatology

A 55-year-old woman with seropositive rheumatoid arthritis, well controlled on etanercept, presents with an acutely painful, cold, blue right foot. CT angiography confirms popliteal arterial thrombosis. ECG and echocardiography identify no cardiac embolic source, and imaging shows neither significant atheroma nor arterial wall changes suggestive of vasculitis. She has never smoked. Before anticoagulation, her activated partial thromboplastin time is prolonged and does not correct on mixing; the dilute Russell's viper venom time is positive. High-titre IgG anticardiolipin and anti-β2-glycoprotein I antibodies remain positive when repeated 13 weeks later. Which diagnosis best explains this presentation?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: D — Antiphospholipid syndrome

The correct answer is antiphospholipid syndrome. She has objectively confirmed arterial thrombosis together with persistent high-titre criterion antiphospholipid antibodies. The prolonged phospholipid-dependent clotting tests, failure to correct on mixing and positive dilute Russell's viper venom time indicate lupus anticoagulant—the apparent anticoagulant effect in vitro is paradoxically associated with thrombosis in vivo. Giant cell arteritis is not supported by inflammatory, cranial or arterial-wall features. Buerger disease predominantly affects smokers and is not associated with this serological profile. Cholesterol embolism usually follows disruption of atherosclerotic plaque and often produces distal multisite disease rather than an isolated large-artery thrombus. Raynaud phenomenon causes episodic vasospasm and does not explain radiologically confirmed arterial thrombosis. Rheumatoid arthritis and etanercept exposure do not supersede the specific thrombotic and serological evidence for APS.

Reference: Barbhaiya M, Zuily S, et al. 2023 ACR/EULAR antiphospholipid syndrome classification criteria. Annals of the Rheumatic Diseases. 2023;82:1258–1270. https://ard.bmj.com/content/82/10/1258