Pneumothorax in Patients with Idiopathic Pleuroparenchymal Fibroelastosis: Incidence, Clinical Features, and Risk Factors.

Background Idiopathic pleuroparenchymal fibroelastosis (PPFE) is a rare form of idiopathic interstitial pneumonia that is characterized by predominantly upper lobe pleural and subpleural lung parenchymal fibrosis. Pneumothorax is one of the major respiratory complications in PPFE patients; however, its clinical features are poorly understood. Objective We aimed to investigate the complication of pneumothorax in patients with idiopathic PPFE. Methods A retrospective multicenter study involving 89 patients who had been diagnosed with idiopathic PPFE was conducted. We investigated the cumulative incidence, clinical features, and risk factors of pneumothorax after the diagnosis of idiopathic PPFE. Results Pneumothorax developed in 53 patients (59.6%) with 120 events during the observation period (41.8 ± 35.0 months). The cumulative incidence of pneumothorax was 24.8, 44.9, and 53.9% at 1, 2, and 3 years, respectively. Most events of pneumothorax were asymptomatic (n = 85; 70.8%) and small in size (n = 92; 76.7%); 30 patients (56.6%) had recurrent pneumothorax. Chest drainage was required in 23 pneumothorax events (19.2%), and a persistent air leak was observed in 13 (56.5%). Patients with pneumothorax were predominantly male and frequently had pathological diagnoses of PPFE and prior history of pneumothorax and corticosteroid use; they also had significantly poorer survival than those without pneumothorax (log-rank test; p = 0.001). Multivariate analysis revealed that a higher residual volume/total lung capacity ratio was significantly associated with the development of pneumothorax after the diagnosis. Conclusion Pneumothorax is often asymptomatic and recurrent in patients with idiopathic PPFE, leading to poor outcomes in some cases.