High prevalence of upper lung field pulmonary fibrosis radiologically consistent with pleuroparenchymal fibroelastosis in patients with round atelectasis

Background Upper-lung field pulmonary fibrosis (upper-PF), radiologically consistent with pleuroparenchymal fibroelastosis (PPFE), was reported to develop in patients with a history of asbestos exposure and tuberculous pleurisy, indicating that chronic pleuritis is correlated with upper-PF development. Round atelectasis reportedly emerges after chronic pleuritis. This study aimed to clarify the association between round atelectasis and upper-PF. Methods We examined the radiological reports of all consecutive patients with round atelectasis between 2006 and 2018 and investigated the incidence of upper-PF development. Results Among 85 patients with round atelectasis, 21 patients (24.7%) were confirmed to finally develop upper-PF lesions. Upper-PF was diagnosed after round atelectasis recognition in more than half of the patients (13/21, 61.9%), whereas upper-PF and round atelectasis were simultaneously detected in the remaining 8 patients. At the time of round atelectasis detection, almost all patients (19/21, 90.5%) had diffuse pleural thickening and round atelectasis was commonly observed in non-upper lobes of 19 patients (90.5%). Fourteen patients had round atelectasis in unilateral lung, and the remaining 7 patients had round atelectasis in bilateral lungs. Among all 14 patients with unilateral round atelectasis, upper-PF developed on the same (n = 11) or both sides (n = 3). Thus, upper-PF emerged on the same side where round atelectasis was present (14/14, 100%). The autopsy of one patient revealed a thickened parietal-visceral pleura suggestive of chronic pleuritis. Subpleural fibroelastosis was also observed. Conclusions Upper-PF occasionally develops on the same side of round atelectasis. Upper-PF may develop as a sequela of chronic pleuritis.