Zeitschrift für medizinische und chirurgische Pathologie
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Two Different Aspects of Pleuroparenchymal Fibroelastosis: A Disease of Pulmonary Fibrosis, and of the Chest Wall

Kentaro Watanabe

The essential histology of PPFE is subpleural fibroelastosis in the upper lobes, which is different from that of usual interstitial pneumonia (UIP). However, PPFE might share a pathologic process leading to end-stage fibrosis with UIP: it might have an antecedent inflammatory or acute lung injury process prior to the development of the thick subleural bands of fibroelastosis, possibly corresponding to a honeycomb lung in UIP. Fibroblastic foci are found in the leading edge of fibroelastosis, and acute exacerbation occurs in patients with PPFE. The numbers of fibroblastic foci might be correlated with acute exacerbation or poor prognosis in patients with PPFE, as in those with UIP.
Flattened thoracic cage and increased ratio of reserve volume/total lung capacity (RV/TLC) are distinctive characteristics seen in patients with PPFE, but not seen in those with UIP. Flattened thoracic cage that occurs secondary to the fibrotic shrinkage of bilateral upper lobes further decreases the distensibility of thoracic cage, restricting the expansion of the lungs and enhancing the atelectatic shrinkage of upper lobes. Such pathophysiology is similar to that of kyphoscoliosis and ankylosing spondylitis. Therapeutic interventions including the use of steroids and antifibrotic agents for patients with PPFE have disappointing results to date. Chest wall mechanics need to be given more attention in the treatment of patients with PPFE.
Heterogeneous clinical background and clinical course of PPFE remind us that PPFE might need to be named “PPFE syndrome” rather than a single disease.