Acute fibrinous and organizing pneumonia in a patient with Sjögren’s syndrome and Legionella pneumonia: a case report and literature review

BACKGROUND: Acute fibrinous and organizing pneumonia (AFOP) is a rare clinicopathological condition. Studies in the literature have reported that AFOP may be associated with respiratory infections, such as respiratory syncytial virus, influenza virus, Pneumocystis jirovecii, Penicillium citrinum, and Chlamydia infections. However, AFOP associated with Legionella infection has not been reported previously. Here, we report a case of a patient with AFOP secondary to Sjögren’s syndrome and Legionella infection. CASE PRESENTATION: A 47-year-old man was admitted to the hospital because of fever, expectoration, and shortness of breath. Lung imaging showed irregular patchy consolidation. A diagnosis of Legionella pneumonia was initially considered on the basis of the patient’s history of exposure to soil before disease onset, signs of extrapulmonary involvement, and a positive Legionella urine antigen test result. However, the patient’s symptoms and lung imaging did not improve after treatment with levofloxacin, moxifloxacin, and tigecycline for Legionella infection. In addition, Sjögren’s syndrome was diagnosed on the basis of clinical manifestations and immunological indicators. Pathological changes associated with AFOP were confirmed from the results of ultrasound-guided percutaneous lung biopsy. The patient’s clinical symptoms improved rapidly after a short course of low-dose corticosteroid therapy, and lung imaging showed significant improvement. CONCLUSIONS: The possibility of secondary AFOP should be considered when Legionella pneumonia does not improve after standard antibiotic therapy. Lung biopsy and histopathological examination are important for the adjustment of treatment strategy. Our case also highlights the importance of screening for autoimmune diseases in patients with AFOP.