Pleuroparenchymal fibroelastosis as a histological background of autoimmune diseases

Patients with autoimmune disease-related interstitial lung disease (AID-ILD) occasionally develop radiologic pleuroparenchymal fibroelastosis (PPFE)-like lesions. However, the significance of AID as an etiology of PPFE has not been fully elucidated. The aim of this study is to verify the increase of elastic fibers in AID-ILD patients and evaluate the prevalence of histological PPFE in patients with AID-ILD. We selected cases of clinically diagnosed AID-ILD and idiopathic pulmonary fibrosis (IPF), in which an autopsy had been performed or in which the patient had undergone pneumonectomy for lung transplantation. We quantified the collagen fibers and elastic fibers in each lobe as the percentage of the non-aerated lung area (collagen fiber score and elastic fiber score, respectively) in histological specimens from a total of 73 patients (AID-ILD, n = 24; IPF, n = 49). There were no significant differences in the collagen fiber scores of the AID-ILD and IPF groups. Meanwhile, the elastic fiber scores of the AID-ILD group were significantly greater than those of the IPF group in the whole lung (17.3 ± 7.70 vs 11.6 ± 4.55), and the upper (16.6 ± 8.11 vs 11.2 ± 5.18), and lower (18.0 ± 9.68 vs 12.0 ± 5.55) lobes (all p < 0.01). Histological PPFE pattern was found in 12 of 24 AID-ILD patients (50%), and histological PPFE pattern as a dominant pattern of fibrosis was found in 2 of the 24 patients (8%). Thus, PPFE can be a manifestation of AID-ILD.