The similarities and differences between pleuroparenchymal fibroelastosis and idiopathic pulmonary fibrosis

The idiopathic form of pleuroparenchymal fibroelastosis (PPFE) is categorized as a rare idiopathic interstitial pneumonia in the current classification. The majority of PPFE cases are idiopathic, but many predisposing factors or comorbidities have been reported. Although histological PPFE is predominantly located in the upper lobes, which are less often affected by fibrosis in patients with idiopathic pulmonary fibrosis (IPF), the clinical course of PPFE is seemingly similar to that of IPF. However, upper lobe fibroelastosis has various clinical and physiological characteristics that differ from those of IPF, including a flattened thoracic cage and a marked decrease in the forced vital capacity (FVC) but with a preserved residual volume. Compared with IPF, the decrease in the walking distance is mild despite the markedly decreased FVC in PPFE, and chest radiograph more frequently shows the elevation of bilateral hilar opacities with or without tracheal deviation. The prognosis may be related to the development of fibrosing interstitial pneumonia in the lower lobes with elevated levels of serum Krebs von den Lungen-6; however, there is marked variation in the pathogenesis and clinical features in PPFE. A proposal of the diagnostic criteria for idiopathic PPFE with and without surgical lung biopsy, which has recently been published, may be useful.

在现行分类中，胸膜肺实质纤维弹性组织增生症（PPFE）特发性类型被归类为一种罕见的特发性间质性肺炎。大多数PPFE病例是特发性的，但已有许多诱发因素或合并症的报道。尽管组织学上PPFE主要位于上叶，而特发性肺纤维化（IPF）患者的上叶较少受纤维化影响，但PPFE的临床病程似乎与IPF相似。然而，上叶纤维弹性组织增生具有多种与IPF不同的临床和生理特征，包括胸廓扁平以及用力肺活量（FVC）显著下降但残气量保留。与IPF相比，尽管PPFE中FVC显著下降，但步行距离的减少较轻微，并且胸部X线片更常显示双侧肺门阴影抬高，伴或不伴气管偏移。预后可能与下叶纤维性间质性肺炎的进展以及血清肺硬化相关蛋白6水平升高有关；然而，PPFE的发病机制和临床特征存在显著差异。最近发表的伴有和不伴有手术肺活检的特发性PPFE诊断标准提案可能是有用的。