BACKGROUNDAcute fibrinous and organizing pneumonia (AFOP) is a unique pathological entity with intra-alveolar fibrin in the form of "fibrin balls" and organizing pneumonia. It was divided into rare idiopathic interstitial pneumonia according to the classification notified by American Thoracic Society/European Respiratory Society in 2013. As a rare pathological entity, it is still not well known and recognized by clinicians. We reviewed the clinical features of 20 patients with AFOP diagnosed in a teaching hospital.

METHODSThe medical records of 20 patients with biopsy-proven diagnosis of AFOP were retrospectively reviewed. The patients' symptoms, duration of the disease, comorbidities, clinical laboratory data, pulmonary function testing, radiographic studies, and the response to treatment were extracted and analyzed.

RESULTSFever was the most common symptom and was manifested in 90% of AFOP patients. For clinical laboratory findings, systematic inflammatory indicators, including C-reactive protein and erythrocyte sedimentation rate, were significantly higher than normal in AFOP patients. In accordance with this increased indicators, injured liver functions were common in AFOP patients. Inversely, AFOP patients had worse clinical conditions including anemia and hypoalbuminemia. For pulmonary function testing, AFOP patients showed the pattern of restrictive mixed with obstructive ventilation dysfunction. For high-resolution computerized tomography (HRCT) findings, the most common pattern for AFOP patients was lobar consolidation which was very similar to pneumonia. However, unlike pneumonia, AFOP patients responded well to glucocorticoids.

CONCLUSIONPatients with AFOP manifest as acute inflammatory-like clinical laboratory parameters and lobar consolidation on HRCT, but respond well to steroid.