Analysis of clinical characteristics of 21 cases of acute fibrinous and organizing pneumonia

Objective: To summarize the clinical features of 21 cases of acute fibrinous and organizing pneumonia (AFOP) confirmed by pathology, thereby improving clinicians' understanding of this disease and avoiding misdiagnosis in clinical practice. Methods: Twenty-one patients diagnosed pathologically with AFOP from January 2016 to April 2019 were analyzed retrospectively. The clinical symptoms, laboratory examination results, imaging features, treatments and outcomes were analyzed comprehensively. Results: There were 10 males and 11 females, with an average age of (58±10) years. All the cases presented subacute disease onset. The main symptoms were cough, expectoration and fever. The results from laboratory examination showed that the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were significantly higher than the normal levels. The total number of leukocytes, the percentage of neutrophils, and procalcitonin were also higher than the normal levels. Among these patients, 4 cases showed positive sputum bacteriology. Nine patients were found to have probable etiological factors (infections in 4, tumors in 4 cases, and connective tissue disease in 1 case). Twelve patients had no confirmed etiological factors. As to radiological findings, the patterns were multiple patchy infiltrates(16/21), solitary mass (3/21) and multiple nodules in both lungs (2/21). Most lesions were subpleural in distribution (15/21), with air bronchogram sign (11/21), pleural effusion (9/21), and cavity (4/21). Three patients received anti-infective therapy only. The infiltration in lung disappeared within 2 months in one patient, but the lesion still existed in one case after three years of follow-up. However, one patient were lost during the follow-up. Eighteen patients were treated with oral glucocorticoids, and about 50% of the patients showed significant improvement in symptoms and imaging findings within one month. The average follow-up time was (22±10) months, and there was no death. Conclusions: The clinical and imaging findings of AFOP are nonspecific. The exact mechanism of its pathogenesis is not clear. Infection and tumor may be related to the pathogenesis of AFOP. AFOP with subacute onset has a good response to glucocorticoid treatment with a better prognosis.