Clinical challengeA 50-year-old man with antiphospholipid syndrome (APS) presents to your office for the first time with a 3-month history of worsening dyspnea, dry cough, and early morning blood-tinged sputum. His APS diagnosis was based on an unprovoked left leg deep vein thrombosis, 4 years prior to the presentation, with persistent (multiple occasions) triple-antiphospholipid antibody (aPL) positivity, defined as lupus anticoagulant (LAC) positivity while not receiving anticoagulation therapy, high-titer (≥80 units) IgG anticardiolipin antibodies (aCL), and high-titer IgG anti-β 2 -glycoprotein I (anti-β 2 GPI). He has no other past medical history, and he is receiving warfarin with a target international normalized ratio (INR) of 2.5-3. Physical examination is normal except for livedo racemosa around his knees. His platelet count is 99 × 10 3 /ml (chronic; fluctuating 80-120 × 10 3 /ml since the APS diagnosis), INR is 3, hemoglobin, creatinine, and complement levels are normal, and spot urine protein:creatinine ratio is 0.3. His primary care physician ordered a chest radiograph, which shows extensive patchy bilateral airspace opacities, and a chest computed tomography (CT) scan, which shows diffuse bilateral ground-glass opacities.