Pleuroparenchymal fibroelastosis diagnosed by multidisciplinary discussions in Japan

Background: Pleuroparenchymal fibroelastosis (PPFE) is a rare subset of idiopathic interstitial pneumonias. No large-scale clinical studies of PPFE have been published. The aim of the study was to clarify the clinical and physiological characteristics of PPFE in Japan Methods: This was a retrospective, nationwide, and multicenter study in Japan. We reviewed 52 patients with PPFE, diagnosed after multidisciplinary discussions. Results: Flat chest index, defined as the ratio of anteroposterior diameter to transverse diameter of thoracic cage at the level of 6th thoracic vertebra, correlated positively with body mass index (BMI) (r=0.340, p=0.013) and percentage of predicted value of forced vital capacity (FVC % pred) (r=0.355, p=0.012), and negatively with the ratio of residual volume to total lung capacity (RV/TLC) (r=-0.312, p=0.042). RV/TLC correlated negatively with BMI (r=-0.746, p < 0.0001) and FVC % pred (r=-0.507, p=0.0005), and positively with age, and physiological variables (GAP) scores (r=0.332, p=0.030). The median survival time and the cumulative 5-year survival rate were 96 months and 58%, respectively. Patients with KL-6 level > 600 (U/mL) survived shorter than those with < 600 (p < 0.001). Conclusion: Low BMI, decreased FVC and increased RV/TLC in PPFE may be related to the progression of flattened chest cage which impairs distension of chest cage at inspiration. Elevated serum levels of KL-6 suggest a poor prognosis of PPFE.