Cryobiopsies are diagnostic in Pleuroparenchymal and Airway-centered Fibroelastosis

TMEM176B Prevents and alleviates bleomycin-induced pulmonary fibrosis via inhibiting transforming growth factor β-Smad signaling

Pulmonary fibrosis is a severe and progressive lung disease characterized by the abnormal accumulation of extracellular matrix, leading to scarring and loss of normal lung function. Recent bioinformatics analysis through the Gene Expression Omnibus (GEO) database identified a significant downregulation of Transmembrane Protein 176B (TMEM176B), previously unexplored in the context of fibrotic lung tissues. To investigate the functional role of TMEM176B, we induced pulmonary fibrosis in mice using bleomycin, TGFβ1, and silica, which consistently resulted in a marked decrease in TMEM176B expression. Intriguingly, overexpression of TMEM176B via adenoviral vectors prior to the induction of fibrosis led to significant improvements in fibrotic manifestations and lung function. Mechanistically, TMEM176B appears to mitigate pulmonary fibrosis by inhibiting the TGFβ1-SMAD signaling pathway, which is a critical mediator of fibroblast proliferation and differentiation and promotes extracellular matrix production. These findings suggest that TMEM176B plays an inhibitory role in the pathophysiological processes of pulmonary fibrosis, highlighting its potential as a therapeutic target.

Two cases of airway-centered fibroelastosis treated with an antifibrotic agent and corticosteroids

Airway-centered fibroelastosis is characterized by peribronchovascular fibroelastosis, predominantly in the upper lobes, with little-to-no pleural involvement. In this study, we describe two cases of airway-centered fibroelastosis diagnosed based on radiological and pathological findings. The first case comprised a 44-year-old man whose forced vital capacity improved over three months following treatment with nintedanib. The second case involved a 50-year-old woman who was treated with oral corticosteroids but yielded an unfavorable outcome. An effective treatment for airway-centered fibroelastosis has not yet been identified; therefore, this study may help contribute to a more thorough discussion regarding treatment strategies for this disease.

Multidisciplinary Approach to the Diagnosis of Idiopathic Interstitial Pneumonias: Focus on the Pathologist's Key Role

Idiopathic Interstitial Pneumonias (IIPs) are a heterogeneous group of the broader category of Interstitial Lung Diseases (ILDs), pathologically characterized by the distortion of lung parenchyma by interstitial inflammation and/or fibrosis. The American Thoracic Society (ATS)/European Respiratory Society (ERS) international multidisciplinary consensus classification of the IIPs was published in 2002 and then updated in 2013, with the authors emphasizing the need for a multidisciplinary approach to the diagnosis of IIPs. The histological evaluation of IIPs is challenging, and different types of IIPs are classically associated with specific histopathological patterns. However, morphological overlaps can be observed, and the same histopathological features can be seen in totally different clinical settings. Therefore, the pathologist's aim is to recognize the pathologic-morphologic pattern of disease in this clinical setting, and only after multi-disciplinary evaluation, if there is concordance between clinical and radiological findings, a definitive diagnosis of specific IIP can be established, allowing the optimal clinical-therapeutic management of the patient.

The world of rare interstitial lung diseases

The world of rare interstitial lung diseases (ILDs) is diverse and complex. Diagnosis and therapy usually pose challenges. This review describes a selection of rare and ultrarare ILDs including pulmonary alveolar proteinosis, pulmonary alveolar microlithiasis and pleuroparenchymal fibroelastosis. In addition, monogenic ILDs or ILDs in congenital syndromes and various multiple cystic lung diseases will be discussed. All these conditions are part of the scope of the European Reference Network on rare respiratory diseases (ERN-LUNG). Epidemiology, pathogenesis, diagnostics and treatment of each disease are presented.

Pleuroparenchymal fibroelastosis

PURPOSE OF REVIEW

Pleuroparenchymal fibroelastosis (PPFE) is a clinico-radiologic-pathologic interstitial lung disease (ILD) characterized by fibrosis that has upper lobe and subpleural predominance, involving both the visceral pleura and the subjacent subpleural lung parenchyma, and comprises dense fibroelastic changes with prominent elastosis of the alveolar walls together with fibrous thickening of the visceral pleura. The goal of this review is to summarize the state-of-the-art understanding in PPFE.

RECENT FINDINGS

PPFE was described in an increasing number of conditions. The course of disease is heterogeneous. Idiopathic PPFE, cases associated with telomerase-related gene mutations, cases related to a history of chemotherapy, and cases combining PPFE with a pattern of usual interstitial pneumonia, may have a particularly poor prognosis. Well-conducted retrospective studies identified marked PPFE features in approximately 10% of patients with idiopathic pulmonary fibrosis, 11% of patients with systemic sclerosis-associated ILD, 6.5% of patients with rheumatoid arthritis-associated ILD, and 23% of patients with hypersensitivity pneumonitis. Drug therapy has not been evaluated prospectively. A small retrospective study suggests that nintedanib may slow disease progression. However, whether the efficacy of antifibrotics is comparable in PPFE and in other forms of progressive pulmonary fibrosis warrants further evaluation.

SUMMARY

Accumulating data indicate that PPFE features are associated with poor prognosis in fibrosing ILDs. Further research on the management of PPFE is warranted.

Pleuroparenchymal Fibroelastosis with a Predominantly Airway-centered Distribution: A Late Complication of Chemotherapy

Airway-centered fibroelastosis is a distinct entity characterized by prominent airway-centered elastosis of the upper lobe with little or no pleural involvement. Little is known regarding its etiology; however, it was reported to have an idiopathic or asthma-associated etiology. We document, for the first time, 2 women (19 and 60 years old) who developed pleuroparenchymal fibroelastosis with a predominantly airway-centered distribution as a late complication (6 and 9 years later, respectively) of chemotherapy. The disease rapidly progressed following the manifestation of symptoms, and they subsequently died (3 and 2 years later, respectively). Therefore, post-chemotherapy long-term monitoring for this disease is warranted.

Pulmonary Fibroelastotic Remodelling Revisited

Pulmonary fibroelastotic remodelling occurs within a broad spectrum of diseases with vastly divergent outcomes. So far, no comprehensive terminology has been established to adequately address and distinguish histomorphological and clinical entities. We aimed to describe the range of fibroelastotic changes and define stringent histological criteria. Furthermore, we wanted to clarify the corresponding terminology in order to distinguish clinically relevant variants of pulmonary fibroelastotic remodelling. We revisited pulmonary specimens with fibroelastotic remodelling sampled during the last ten years at a large European lung transplant centre. Consensus-based definitions of specific variants of fibroelastotic changes were developed on the basis of well-defined cases and applied. Systematic evaluation was performed in a steps-wise algorithm, first identifying the fulcrum of the respective lesions, and then assessing the morphological changes, their distribution and the features of the adjacent parenchyma. We defined typical alveolar fibro-elastosis as collagenous effacement of the alveolar spaces with accompanying hyper-elastosis of the remodelled and paucicellular alveolar walls, independent of the underlying disease in 45 cases. Clinically, this pattern could be seen in (idiopathic) pleuroparenchymal fibro-elastosis, interstitial lung disease with concomitant alveolar fibro-elastosis, following hematopoietic stem cell and lung transplantation, autoimmune disease, radio-/chemotherapy, and pulmonary apical caps. Novel in-transit and activity stages of fibroelastotic remodelling were identified. For the first time, we present a comprehensive definition of fibroelastotic remodelling, its anatomic distribution, and clinical associations, thereby providing a basis for stringent patient stratification and prediction of outcome.

Pleuroparenchymal fibroelastosis: Clinical, radiological and histopathological features

Pleuroparenchymal fibroelastosis (PPFE) is a rare, generally idiopathic form of interstitial pneumonia with unique clinical, radiological and histopathological features. It is named after the presence of upper lobe pleural and subjacent parenchymal fibrosis, with accompanying elastic fibers. Although it is usually an idiopathic disease, it has been linked to other co-existent diseases. Diagnostic suspicion of PPFE is based on the identification of typical abnormalities on chest CT scan, which are prevailingly located in the upper lobes, adjacent to the apex of the lungs. Diagnosis can be confirmed by histological analysis, although biopsy is not always feasible. The disease is generally progressive, but not uniformly. The course of the disease is frequently slow and involves a progressive loss of upper lobe volume, which results in platythorax, associated with a significant reduction of body mass. PPFE concomitant to other interstitial lung diseases is associated with a poorer prognosis. The disease occasionally progresses rapidly causing irreversible respiratory insufficiency, which leads to death. Currently, there is no effective pharmacological therapy available, and lung transplantation is the best therapeutic option. The purpose of this review is to draw the attention to PPFE, describe its clinical, radiological and histopathological features, analyze its diagnostic criteria, and provide an update on the management of the disease.

The pathogenesis and pathology of idiopathic pleuroparenchymal fibroelastosis

Idiopathic pleuroparenchymal fibroelastosis (IPPFE) is a rare subtype of idiopathic interstitial pneumonias that consists of elastofibrosis involving the lung parenchyma and pleural collagenous fibrosis predominantly located in the upper lobes. IPPFE has various distinct clinical and physiological characteristics, including platythorax and a marked decrease of forced vital capacity with an increased residual volume on a respiratory function test. The concept of IPPFE is now widely recognized and some diagnostic criteria have been proposed. In addition, the accumulation of cases has revealed the pathological features of IPPFE. However, little is known about the pathogenesis or the process of disease formation in IPPFE. This review article will provide a summary of the pathological features and previously reported hypotheses on disease formation in IPPFE, to discuss the potential etiologies and pathogenesis of IPPFE.

Pleuroparenchymal Fibroelastosis. A Review of Clinical, Radiological, and Pathological Characteristics

Pleuroparenchymal fibroelastosis (PPFE) is an unusual pulmonary disease with unique clinical, radiological, and pathological characteristics. Designated a rare idiopathic interstitial pneumonia in 2013, its name refers to a combination of fibrosis involving the visceral pleura and fibroelastotic changes predominating in the subpleural lung parenchyma. Although a number of disease associations have been described, no single cause of PPFE has been unequivocally identified. A diagnosis of PPFE is most commonly achieved by identifying characteristic abnormalities on computed tomographic scans. The earliest changes are consistently located in the upper lobes close to the lung apices, the same locations where subsequent disease progression is also most conspicuous. When sufficiently severe, the disease leads to progressive volume loss of the upper lobes, which, in combination with decreased body mass, produces platythorax. Once regarded as a slowly progressing entity, it is now acknowledged that some patients with PPFE follow an inexorably progressive course that culminates in irreversible respiratory failure and early death. In the absence of effective medical drug treatment, lung transplant remains the only therapeutic option for this disorder. This review focuses on improving early disease recognition and evaluating its pathophysiological impact and discusses working approaches for its management.

Pleuroparenchymal fibroelastosis (PPFE) treated with lung transplantation and review of the literature

A 26-year-old woman presented with a 15-year history of non-progressive dyspnoea. Chest imaging showed bilateral apical pleural and parenchymal scarring, pleural thickening and bronchiectasis. Pulmonary function tests showed a moderate restrictive defect. Non-invasive workup was non-revealing; therefore, the patient was referred for video-assisted thoracic surgery and lung biopsy. Histopathology revealed pleural thickening and, subpleural parenchymal fibrosis and elastic tissue deposition. Lung parenchyma further away from the pleura was well preserved. Based on these findings, the patient was diagnosed with pleuroparenchymal fibroelastosis (PPFE). Since PPFE is a progressive disorder without effective medical therapies, and given our patient's worsening symptoms, she underwent bilateral lung transplantation. It has been almost 4 years since the lung transplantation, our patient continues to do well. To the best of our knowledge, to date, this is the longest follow-up reported for a PPFE patient undergoing lung transplantation.