Restrictive allograft syndrome and idiopathic pleuroparenchymal fibroelastosis: do they really have the same histology?

Aims Restrictive Allograft Syndrome (RAS) and idiopathic pleuroparenchymal fibroelastosis (IPPFE) are two different diseases reported to share the same histology. RAS relates to chronic allograft dysfunction in lung transplantation with IPPFE being a rare condition in native lungs. Our aim is to compare their histologies, alongside biopsies of usual interstitial pneumonia (UIP), to determine if there are differences that might help to elucidate the pathogenesis. Methods and Results We selected 4 post-mortem allograft lungs from patients who developed clear clinical RAS pattern, 5 biopsies diagnosed as IPPFE, 5 UIP biopsies and 5 sections of normal lung. Histopathologic features were described without knowledge of clinical and radiological features. Both RAS allografts and IPPFE biopsies showed intra-alveolar fibrosis and elastosis (IAFE), but RAS allografts also showed concomitant obliterative bronchiolitis, vascular lymphoplasmacytic inflammation within fibro-intimal thickening, less fibroblastic foci at the advancing edge of the fibrosis (1 against 14.4 FF in 2mm2) and a slight reduction of the capillary network compared to UIP (p=0.07) and controls (p=0.06). The main differences seen in UIP were the lack of IAFE and the presence of honeycomb change. Conclusions RAS and PPFE histopathology both show IAFE, but display various differences, particularly in their vascular morphology that may allow further understanding of pathogenesis. This article is protected by copyright. All rights reserved.