Extent of pulmonary fibrosis on high-resolution computed tomography is a prognostic factor in patients with pleuroparenchymal fibroelastosis

Proposed Clinical Algorithm for Pleuroparenchymal Fibroelastosis (PPFE)

Pleuroparenchymal fibroelastosis (PPFE) is characterized by fibrosis involving the pleura and subpleural lung parenchyma, predominantly in the upper lobes. As PPFE appears to occur in patients with heterogeneous etiologies, the disease course is thus also heterogenous, with some patients showing rapid progression while others have slow progression. Therefore, it is very difficult to predict prognosis with PPFE. Needless to say, this problematic matter has influenced the treatment strategy of PPFE patients. In fact, until now no evidence has been shown for use in creating an appropriate management algorithm for PPFE. We speculate that "uncoordinated breathing" is the most important reason for dyspnea in PPFE patients. Because monitoring of physique and not just pulmonary function and radiological evaluation is also very important, particularly in PPFE patients, this review focused on the characteristics of PPFE through an overview of previous studies in this field, and we proposed an algorithm as precision medicine based on the current evidence. Multiple views by the pulmonologist are needed to standardize a clinical algorithm that is necessary to correctly assess PPFE patients under the premise of maintenance of physique by providing appropriate nutritional care and pulmonary rehabilitation.

Partial pressure of carbon dioxide levels reflect disease severity in idiopathic pleuroparenchymal fibroelastosis

BACKGROUND

Hypercapnia can cause a disturbance of consciousness and adversely affect a patient's general condition. Patients with interstitial lung disease seldom experience hypercapnia. Hypercapnia is a typical phenomenon in patients with pleuroparenchymal fibroelastosis (PPFE), especially in advanced stages. However, the clinical significance of hypercapnia in patients with idiopathic PPFE (iPPFE) has not been studied in detail.

METHODS

We retrospectively selected patients with iPPFE who had undergone blood gas analysis. The first blood gas data obtained after iPPFE diagnosis were examined. The partial pressure of carbon dioxide (PCO₂) levels and their association with characteristic iPPFE parameters, including the flat chest index (the ratio of the anteroposterior diameter of the thoracic cage to the transverse diameter of the thoracic cage), were investigated.

RESULTS

A total of 47 patients with iPPFE were included in this study. The PCO₂ level was moderately and inversely correlated with the forced vital capacity. (r = -0.431, P = 0.014), flat chest index (r = -0.497, P < 0.001), and body mass index (r = -0.313, P = 0.038) and was positively correlated with residual volume/total lung capacity. (r = 0.514, P < 0.01). A higher PCO₂ level was also significantly associated with poorer prognosis in patients with iPPFE.

CONCLUSIONS

PCO₂ levels could be used as an indicator of disease severity in patients with iPPFE.

Acute exacerbation of pleuroparenchymal fibroelastosis with lower lobe usual interstitial pneumonia: An autopsy case

An 87-year-old man presented with dyspnea. Computed tomography revealed progressive subpleural consolidation in the apex, reticular shadows in the lower lobes, and bilateral ground glass opacifications. He died of respiratory failure on day 3. The post-mortem examination showed exudative stage diffuse alveolar damage and pulmonary edema. Intraalveolar collagenous fibrosis and subpleural elastosis were observed in the upper lobes, accompanied by interlobular septal and pleural thickening and lung architecture remodeling in the lower lobes. He was diagnosed with acute exacerbation of pleuroparenchymal fibroelastosis with lower lobe usual interstitial pneumonia, which can be fatal.

Prediction model for patient prognosis in idiopathic pulmonary fibrosis using hybrid radiomics analysis

Objectives

To develop an imaging prognostic model for idiopathic pulmonary fibrosis (IPF) patients using hybrid auto-segmentation radiomics analysis, and compare the predictive ability between the radiomics analysis and conventional visual score methods.

Methods

Data from 72 IPF patients who had undergone CT were analyzed. In the radiomics analysis, quantitative CT analysis was performed using the semi-auto-segmentation method. In the visual method, the extent of radiologic abnormalities was evaluated and the overall percentage of lung involvement was calculated by averaging values for six lung zones. Using a training cohort of 50 cases, we generated a radiomics model and a visual score model. Subsequently, we investigated the predictive ability of these models in a testing cohort of 22 cases.

Results

Three significant prognostic factors such as contrast, Idn, and cluster shade were selected by LASSO Cox regression analysis. In the visual method, multivariate Cox regression analysis revealed that honeycombing and reticulation were significant prognostic factors. Subsequently, a predictive nomogram for prognosis in IPF patients was established using these factors. In the testing cohort, the c-index of the visual and radiomics nomograms were 0.68 and 0.74, respectively. When dividing the cohort into high-risk and low-risk groups using the median nomogram score, significant differences in overall survival (OS) in the visual and radiomics models were observed (P=0.000 and P=0.0003, respectively).

Conclusions

The prediction model with hybrid radiomics analysis had a better ability to predict OS in IPF patients than that of the visual method.

Idiopathic pleuroparenchymal fibroelastosis

The term idiopathic pleuroparenchymal fibroelastosis refers to a rare interstitial lung disease that predominantly involves the upper lobes. It has been considered a rare subtype of interstitial lung disease since 2013, when it was included in the joint consensus statement on the diagnosis of interstitial lung diseases published by the American Thoracic Society (ATS) and the European Respiratory Society (ERS). Currently, two distinct types of pleuroparenchymal fibroelastosis are recognized: the idiopathic type for cases in which it has not been possible to establish a specific etiology and a secondary type associated with a variety of different causes. The diagnosis of pleuroparenchymal fibroelastosis must be managed from a combined clinical and radiological perspective. High-resolution computed tomography (HRCT) is the imaging method of choice for the evaluation and diagnosis of pleuroparenchymal fibroelastosis. In many cases, the diagnosis will be based exclusively on the HRCT findings and histologic confirmation will be unnecessary. This article describes the clinical, radiological, and histological characteristics of pleuroparenchymal fibroelastosis, discussing the different associations with this entity and its differential diagnosis.

Impact of sleep-related hypoventilation in patients with pleuroparenchymal fibroelastosis

BACKGROUND

Pleuroparenchymal fibroelastosis (PPFE) is a rare fibrosing lung disease with a predilection for the upper lobe and its progression causes hypoventilation, resulting in hypercapnia. Even though the association between sleep-related hypoventilation (SRH) and chronic obstructive pulmonary disease was well documented, its impact in patients with PPFE was not evaluated. The aim of this study is to clarify the impact of SRH on prognosis in PPFE.

METHODS

A retrospective review of the medical records of 52 patients with PPFE who underwent transcutaneous carbon dioxide monitoring during sleep was done. Patients were stratified into SRH (n = 28) and non-SRH (n = 24) groups based on American Academy of Sleep Medicine criteria. The impact of SRH on the prognosis of PPFE, as well as the clinical factors and comorbidities of PPFE associated with SRH, were evaluated.

RESULTS

Forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), total lung capacity (TLC), and carbon monoxide diffusing capacity (DLco) in the SRH group were significantly lower than the non-SRH group (P < .01). Chronic pulmonary aspergillosis (CPA) was found at a higher rate in the SRH group (P = .02). The median survival time for SRH patients was 330 days, whereas roughly 80% of non-SRH patients were alive during the 3-year observation period (P < .01). Body mass index was a significant prognostic factor in PPFE patients with SRH (HR .78; 95% CI; .64-.94; P < .01). Home oxygen therapy (HOT) during the day and noninvasive positive pressure ventilation (NPPV) at night while sleeping tended to improve prognosis in the SRH group, as indicated by HR of .25 (P = .07).

CONCLUSIONS

SRH may be a poor prognostic factor for PPFE. Additionally, SRH may modify susceptibility to Aspergillosis in patients with PPFE. HOT plus NPPV may improve the disease outcomes in patients with SRH.

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.

Platythorax progresses with lung involvement in pleuroparenchymal fibroelastosis

BACKGROUND

Patients diagnosed with pleuroparenchymal fibroelastosis (PPFE) exhibit unique clinical features, including upper lobe-dominant lung involvement and platythorax (or flattened thoracic cage). Although platythorax have been shown to be a sign of disease progression, the temporal relationship between the progression of platythorax and the extent of lung involvement has not been closely investigated.

METHODS

We retrospectively investigated patients diagnosed with PPFE, who did not exhibit fibrotic lesions other than PPFE in the lower lobes. We estimated the fibrosis score, which is a visual score indicating the percentage of lung parenchyma occupied by the disease on computed tomography images selected every 2 cm from the lung apex to the lung base, and the flat chest index (the ratio of the anteroposterior diameter of the thoracic cage to the transverse diameter of the thoracic cage). Additionally, we investigated serial changes in the flat chest index and fibrosis score.

RESULTS

A total of 29 patients were included in this study. The fibrosis score was found to be weakly and inversely correlated with forced vital capacity %predicted at the diagnosis (r = -0.40, p = 0.038). Furthermore, the annual changes in the flat chest index and fibrosis score was found to be moderately and inversely correlated (r = -0.663, p = 0.0037).

CONCLUSIONS

These results indicate that there is a causal relationship between the progression of fibroelastosis and that of platythorax in patients with PPFE.

A proposed prognostic prediction score for pleuroparenchymal fibroelastosis

BACKGROUND

Clinical course of pleuroparenchymal fibroelastosis (PPFE) shows considerable variation among patients, but there is no established prognostic prediction model for PPFE.

METHODS

The prediction model was developed using retrospective data from two cohorts: our single-center cohort and a nationwide multicenter cohort involving 21 institutions. Cox regression analyses were used to identify prognostic factors. The total score was defined as the weighted sum of values for the selected variables. The performance of the prediction models was evaluated by Harrell's concordance index (C-index). We also examined the usefulness of the gender-age-physiology (GAP) model for predicting the prognosis of PPFE patients.

RESULTS

We examined 104 patients with PPFE (52 cases from each cohort). In a multivariate Cox analysis, a lower forced vital capacity (FVC [defined as FVC < 65%]; hazard ratio [HR], 2.23), a history of pneumothorax (HR, 3.27), the presence of a lower lobe interstitial lung disease (ILD) (HR, 2.31), and higher serum Krebs von den Lungen-6 (KL-6) levels (> 550 U/mL, HR, 2.56) were significantly associated with a poor prognosis. The total score was calculated as 1 × (FVC, < 65%) + 1 × (history of pneumothorax) + 1 × (presence of lower lobe ILD) + 1 × (KL-6, > 550 U/mL). PPFE patients were divided into three groups based on the prognostic score: stage I (0-1 points), stage II (2 points), and stage III (3-4 points). The survival rates were significantly different in each stage. The GAP stage was significantly associated with the prognosis of PPFE, but no difference was found between moderate (stage II) and severe (stage III) disease. Our new model for PPFE patients (PPFE Prognosis Score) showed better performance in the prediction of mortality in comparison to the GAP model (C-index of 0.713 vs. 0.649).

CONCLUSIONS

Our new model for PPFE patients could be useful for predicting their prognosis.

Pleuroparenchymal fibroelastosis in Mycobacterium avium complex pulmonary disease: clinical characteristics and prognostic impact

The association between Mycobacterium avium complex pulmonary disease (MAC-PD) and pleuroparenchymal fibroelastosis (PPFE) has been reported previously, and interstitial pneumonia as a comorbidity is associated with a worse prognosis. However, no study has thoroughly reported on PPFE associated with MAC-PD. The present study investigated the prevalence, clinical characteristics, and prognostic impact of PPFE in patients with MAC-PD. A total of 224 patients, newly diagnosed with MAC-PD, were retrospectively reviewed. At the time of diagnosis, chest high-resolution computed tomography (HRCT), sputum examination, and clinical characteristics were collected. The extent of PPFE and MAC-PD was evaluated semi-quantitatively using HRCT scores. Risk factor analysis for clinical or radiological deterioration necessitating multidrug antimicrobial treatment within 3 years, and all-cause mortality within 5 years, from the initial diagnosis was performed based on the PPFE score. PPFE was observed in 59 out of 224 patients (26.3%). A higher PPFE score was a risk factor for dyspnoea, fatigue, and lower body mass index (BMI) (p<0.05). Although PPFE score did not correlate with clinical or radiological deterioration within 3 years (p=0.576), a higher PPFE score (adjusted OR 1.66, 95% CI 1.06-2.60, p=0.028) and lower BMI (adjusted OR 0.61, 95% CI 0.39-0.94, p=0.028) increased the risk of 5-year mortality. PPFE is a relatively common complication and an independent poor prognostic factor of MAC-PD. This study highlights the need for further studies investigating whether the presence of PPFE can be a clinical indicator for initiating treatment of MAC-PD.