Abstract
BACKGROUND: Cryptogenic organizing pneumonia (COP), a rare interstitial lung disease, can mimic community-acquired pneumonia (CAP), often leading to delayed diagnosis. This case highlights the importance of recognizing COP in elderly patients and brings attention to pulmonary embolism (PE) as a potential but underrecognized complication associated with glucocorticosteroid therapy, providing novel insights into hypercoagulability risks during treatment. CASE PRESENTATION: An 80-year-old woman from Xinjiang presented with a 4-week history of cough, dyspnea, and weight loss that was unresponsive to antibiotics. Chest Computed tomography (CT) revealed bilateral subpleural consolidations with air bronchograms. Bronchoscopy ruled out infection, and a multidisciplinary evaluation confirmed COP based on clinical, radiological, and pathological correlation. Oral prednisone at 0.75 mg/kg/day led to symptom resolution within 14 days. However, during steroid tapering (10% weekly reduction), she developed hypoxemia at 3 months. CT angiography revealed segmental PE, despite the absence of conventional thrombosis risk factors. Treatment with anticoagulation and continued glucocorticoid therapy resulted in full recovery after 6 months. CONCLUSIONS: Clinicians should consider COP in elderly patients with pneumonia unresponsive to antibiotics, confirm the diagnosis through biopsy, and remain vigilant for hypercoagulable states during glucocorticoid tapering. Anticoagulation should be tailored even in the absence of traditional thrombosis risk factors. The temporal association between steroid tapering and PE suggests that glucocorticoids may modulate endothelial function and coagulation pathways, highlighting the need for mechanistic studies to inform thromboembolic surveillance in COP management.