Pulmonary interstitial emphysema is a risk factor for poor prognosis and a cause of air leaks

Background: Pulmonary interstitial emphysema is a rare, abnormal condition in which air pressure from the alveolar airspace tears the adjacent interstitial tissues of the lung and causes the formation of cystic spaces. Pulmonary interstitial emphysema is a known indication for mechanical ventilation in premature infants with neonatal respiratory distress syndrome, and it can be observed in various types of interstitial lung disease. Nevertheless, its pathogenesis and clinical impact remain unknown. Methods: We reviewed data from 433 cases of interstitial lung disease from an external consultation archive. Multidisciplinary diagnosis along with clinical and follow-up data, including events of air leaks such as pneumothorax and mediastinal emphysema, were obtained and compared to those of 150 control cases of interstitial lung disease without pulmonary interstitial emphysema. Results: We found 22 (5.1%) cases of interstitial lung disease with pulmonary interstitial emphysema. The diagnoses included idiopathic pulmonary fibrosis (5/22 [22.7%]), pleuroparenchymal fibroelastosis (4/22 [18.2%]), chronic hypersensitivity pneumonia (4/22 [18.2%]), and others (9/22 [40.9%]). Cases involving pulmonary interstitial emphysema demonstrated a significantly higher frequency of air leaks than did those without pulmonary interstitial emphysema (12/22 [54.5%] versus 23/150 [15.3%]; P < 0.001; odds ratio, 6.63) and were associated with worse prognosis (P = 0.009 [log-rank]) and a lower median percent forced vital capacity (73.2% versus 84.0%; P < 0.001). Conclusions: We found that pulmonary interstitial emphysema is an independent factor for poor prognosis, which also shows a trend to cause air leaks, including pneumothorax and mediastinal emphysema.