Idiopathic pleuroparenchymal fibroelastosis: A review of the previous literature and current knowledge.

Idiopathic pleuroparenchymal fibroelastosis (iPPFE) is characterized by upper lobe-dominant fibrosis involving the pleura and subpleural lung parenchyma. Pathologically, it is characterized by parenchymal intra-alveolar fibrosis with marked deposition of elastic fibers and dense thickening of the visceral pleura. Since iPPFE was categorized as a rare idiopathic interstitial pneumonia (IIP) by the America Thoracic Society/European Respiratory Society, several studies have been conducted, revealing an overall picture of iPPFE in terms of epidemiology, clinical manifestations, and mortality, in addition to its radiological and histological characteristics. Subsequently, several clinical diagnostic criteria that were not necessary for pathological analyses were proposed. Further, the underlying diseases responsible for secondary PPFE and PPFE-like lesions and their clinical implications were delineated. Typically, patients with iPPFE exhibit lean body stature together with platythorax, as well as relatively severe impairment of pulmonary function. In addition to upper-lobe PPFE lesions, lower-lobe interstitial lung disease (ILD) is commonly observed in patients with iPPFE, with the usual interstitial pneumonia pattern being most frequent. These distinct features of iPPFE were mostly associated with mortality, resulting in a poor prognosis relative to fibrotic ILD. Despite increased knowledge regarding the clinical characteristics of iPPFE, no effective therapy has been established other than lung transplantation. The efficacy of antifibrotic therapy, nutrition intervention, and pulmonary rehabilitation has not been determined. This article reviews previous studies and discusses the etiology, clinical manifestations, mortality risk, and treatment of iPPFE.