Airway-centered interstitial fibrosis: etiology, clinical findings and prognosis

Rare interstitial lung diseases: a narrative review

Background and Objective

Interstitial lung diseases (ILDs) encompass over 200 entities. Among them, fibrosing lung diseases, have recently generated special interest due to the emerging therapies for their management. However, it is important to deepen our knowledge of other less prevalent ILD, since many of them are associated with a poor prognosis. This narrative review aims to provide a practical and up-to-date description of some poorly recognized ILD. It covers rare idiopathic interstitial pneumonias and their histologic patterns, genetic disorders with interstitial lung involvement (Hermansky-Pudlak syndrome), and ILD associated with benign proliferation of pulmonary lymphoid tissue, namely follicular bronchiolitis and granulomatous-lymphocytic interstitial lung disease.

Methods

Electronic searches of PubMed and Google Scholar using specific keywords were conducted. Articles underwent screening for relevance, covering review articles, meta-analyses, systematic reviews, case series, prospective studies, society guidelines, editorials in peer-reviewed journals; scientific books on the subject. The data included was limited to English and Spanish publications.

Key Content and Findings

Despite the low prevalence of these diseases, the increased recognition of radiological patterns, pathological features, and diagnostic procedures, have permitted their better characterization. This review highlights epidemiology, clinical presentation, diagnosis, natural history, and treatment.

Conclusions

Lesser-studied ILD represent a diagnostic and therapeutic challenge and can be frequently misdiagnosed. Also, due to the lack of randomized controlled trials, there are no well-established therapeutic options. Further studies or registries are needed to improve accurate diagnosis and management.

Central Role of CT in Management of Pulmonary Fibrosis

With the approval of antifibrotic medications to treat patients with idiopathic pulmonary fibrosis and progressive pulmonary fibrosis, radiologists have an integral role in diagnosing these entities and guiding treatment decisions. CT features of early pulmonary fibrosis include irregular thickening of interlobular septa, pleura, and intralobular linear structures, with subsequent progression to reticular abnormality, traction bronchiectasis or bronchiolectasis, and honeycombing. CT patterns of fibrotic lung disease can often be reliably classified on the basis of the CT features and distribution of the condition. Accurate identification of usual interstitial pneumonia (UIP) or probable UIP patterns by radiologists can obviate the need for a tissue sample-based diagnosis. Other entities that can appear as a UIP pattern must be excluded in multidisciplinary discussion before a diagnosis of idiopathic pulmonary fibrosis is made. Although the imaging findings of nonspecific interstitial pneumonia and fibrotic hypersensitivity pneumonitis can overlap with those of a radiologic UIP pattern, these entities can often be distinguished by paying careful attention to the radiologic signs. Diagnostic challenges may include misdiagnosis of fibrotic lung disease due to pitfalls such as airspace enlargement with fibrosis, paraseptal emphysema, recurrent aspiration, and postinfectious fibrosis. The radiologist also plays an important role in identifying complications of pulmonary fibrosis-pulmonary hypertension, acute exacerbation, infection, and lung cancer in particular. In cases in which there is uncertainty regarding the clinical and radiologic diagnoses, surgical biopsy is recommended, and a multidisciplinary discussion among clinicians, radiologists, and pathologists can be used to address diagnosis and management strategies. This review is intended to help radiologists diagnose and manage pulmonary fibrosis more accurately, ultimately aiding in the clinical management of affected patients. ©RSNA, 2024 Supplemental material is available for this article.

Airway injury induces alveolar epithelial and mesenchymal responses mediated by macrophages

Acute injury in the airways or the lung activates local progenitors and stimulates changes in cell-cell interactions to restore homeostasis, but it is not appreciated how more distant niches are impacted. We utilized mouse models of airway-specific epithelial injury to examine secondary tissue-wide alveolar, immune, and mesenchymal responses. Single-cell transcriptomics and in vivo validation revealed transient, tissue-wide proliferation of alveolar type 2 (AT2) progenitor cells after club cell-specific ablation. The AT2 cell proliferative response was reliant on alveolar macrophages (AMs) via upregulation of Spp1 which encodes the secreted factor Osteopontin. A previously uncharacterized mesenchymal population we termed Mesenchymal Airway/Adventitial Niche Cell 2 (MANC2) also exhibited dynamic changes in abundance and a pro-fibrotic transcriptional signature after club cell ablation in an AM-dependent manner. Overall, these results demonstrate that acute airway damage can trigger distal lung responses including altered cell-cell interactions that may contribute to potential vulnerabilities for further dysregulation and 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.

Impact of concomitant gastroesophageal reflux disease symptomology on prognosis and pulmonary function of chronic hypersensitivity pneumonitis

Background and Objectives

Comorbid risk factors in chronic hypersensitivity pneumonitis (CHP) are poorly characterised. Gastroesophageal reflux disease (GERD) is linked to interstitial lung diseases like idiopathic pulmonary fibrosis (IPF), but its association and treatment in CHP is less understood. This study aims to understand the role and prevalence of GERD in CHP, plus the effect of GERD treatment on lung function and mortality.

Methods

A tertiary referral centre panel was retrospectively reviewed for 214 patients diagnosed with CHP based on clinical history, bronchoalveolar lavage fluid analysis, imaging and histopathology. GERD diagnostic criteria included symptomology, acid suppressive therapy use and diagnostic testing. CHP patients with GERD (n = 89) and without GERD (n = 125) were compared via descriptive statistical analysis. Pulmonary function, GERD diagnosis plus treatment and other comorbidities were evaluated against CHP outcomes.

Results

Respective differences between diagnosis and study termination dates in the GERD population versus without GERD for functional vital capacity (FVC) were - 1 L vs - 2.5 L, diffusing capacity of the lungs for carbon monoxide (DLCO) were - 2 mL/min/mmHg versus - 1 mL/min/mmHg, per cent alive at the time of study 88% versus 81%, median date of survival 574.5 versus 850 and supplemental oxygen requirement 41% versus 37%. GERD prevalence was higher in CHP patients relative to the general population. No statistical significance was found between survival curves, oxygen requirement, smoking history, FVC, or DLCO.

Conclusions

GERD could be a harmful comorbidity in CHP though may not necessarily affect survival or functional outcomes. This aligns with previous IPF studies, though remains controversial. Further research is needed regarding this association and treatment benefit.

A roadmap for developing and engineering in vitro pulmonary fibrosis models

Idiopathic pulmonary fibrosis (IPF) is a severe form of pulmonary fibrosis. IPF is a fatal disease with no cure and is challenging to diagnose. Unfortunately, due to the elusive etiology of IPF and a late diagnosis, there are no cures for IPF. Two FDA-approved drugs for IPF, nintedanib and pirfenidone, slow the progression of the disease, yet fail to cure or reverse it. Furthermore, most animal models have been unable to completely recapitulate the physiology of human IPF, resulting in the failure of many drug candidates in preclinical studies. In the last few decades, the development of new IPF drugs focused on changes at the cellular level, as it was believed that the cells were the main players in IPF development and progression. However, recent studies have shed light on the critical role of the extracellular matrix (ECM) in IPF development, where the ECM communicates with cells and initiates a positive feedback loop to promote fibrotic processes. Stemming from this shift in the understanding of fibrosis, there is a need to develop in vitro model systems that mimic the human lung microenvironment to better understand how biochemical and biomechanical cues drive fibrotic processes in IPF. However, current in vitro cell culture platforms, which may include substrates with different stiffness or natural hydrogels, have shortcomings in recapitulating the complexity of fibrosis. This review aims to draw a roadmap for developing advanced in vitro pulmonary fibrosis models, which can be leveraged to understand better different mechanisms involved in IPF and develop drug candidates with improved efficacy. We begin with a brief overview defining pulmonary fibrosis and highlight the importance of ECM components in the disease progression. We focus on fibroblasts and myofibroblasts in the context of ECM biology and fibrotic processes, as most conventional advanced in vitro models of pulmonary fibrosis use these cell types. We transition to discussing the parameters of the 3D microenvironment that are relevant in pulmonary fibrosis progression. Finally, the review ends by summarizing the state of the art in the field and future directions.

The prognostic value of gastroesophageal reflux disorder in interstitial lung disease related hospitalizations

Background

Gastroesophageal reflux disease (GERD) is a common comorbidity in patients with interstitial lung disease (ILD). We built and validated a model using the national inpatient sample (NIS) database to assess the contributory role of GERD in ILD-related hospitalizations mortality.

Methods

In this retrospective analysis, we extracted ILD-related hospitalizations data between 2007 and 2019 from the NIS database. Univariable logistic regression was used for predictor selection. Data were split into the training and validation cohorts (0.6 and 0.4, respectively). We used decision tree analysis (classification and regression tree, CART) to create a predictive model to explore the role of GERD in ILD-related hospitalizations mortality. Different metrics were used to evaluate our model. A bootstrap-based technique was implemented to balance our training data outcome to improve our model metrics in the validation cohort. We conducted a variance-based sensitivity analysis to evaluate GERD's importance in our model.

Findings

The model had a sensitivity of 73.43%, specificity of 66.15%, precision of 0.27, negative predictive value (NPV) of 93.62%, accuracy of 67.2%, Matthews Correlation Coefficient (MCC) of 0.3, F1 score of 0.4, and area under the curve (AUC) for the receiver operating characteristic (ROC) curve of 0.76. GERD did not predict survival in our cohort. GERD contribution to the model was ranked the eleventh among twenty-nine variables included in this analysis (importance of 0.003, normalized importance of 5%). GERD was the best predictor in ILD-related hospitalizations who didn’t receive mechanical ventilation.

Interpretations

GERD is associated with mild ILD-related hospitalization. Our model-performance measures suggest overall an acceptable discrimination. Our model showed that GERD does not have a prognostic value in ILD-related hospitalization, indicating that GERD per se might not have any impact on mortality in hospitalized ILD patients.

Fibrosing Interstitial Lung Disease in Children: An HRCT-Based Analysis

OBJECTIVE

To determine high resolution CT (HRCT) patterns of pulmonary fibrosis (PF) in children; and their etiological correlates.

METHODS

This was a retrospective study involving 149 children with diffuse lung disease (DLD). Patterns of involvement were classified based on dominant lung finding as ground glass opacity (GGO) dominant, nodule dominant, cystic lung disease, or PF. Patterns of PF were classified based on distribution and morphology into airway centric fibrosis (ACF), subpleural fibrosis (SPF), progressive massive fibrosis (PMF) and fibrocavitary. A comparison was made between the two dominant groups for apicobasal distribution, associated findings (GGO, nodules, cysts), and pulmonary artery hypertension (PAH).

RESULTS

Nineteen patients showed PF on HRCT. ACF was commonest (52.6%), followed by SPF (42.1%). The common etiology was sarcoidosis (30%) in ACF, and connective tissue disorders (CTD) (50%) in SPF. Significant difference was found between ACF and SPF in apicobasal distribution (p = 0.04), presence of nodules (p = 0.03), and cysts (p = 0.02).

CONCLUSION

PF may present as an end stage of several childhood lung diseases. PF on imaging has discernible morphological patterns that correlate with underlying etiology.

Peribronchiolar Metaplasia: A Marker of Cigarette Smoke-Induced Small Airway Injury in a Rural Cohort

Background

Peribronchiolar metaplasia (PBM) is considered a reaction to injury characterized by the proliferation of bronchiolar epithelium into immediately adjacent alveolar walls. While an association of PBM with diffuse interstitial lung diseases has been recognized, the clinical significance of PBM remains uncertain.

Methods

A cohort (n = 352) undergoing surgical resection of a lung nodule/mass in a rural area was retrospectively reviewed. Multivariate logistic regression analysis was performed to determine the association of PBM with clinical, physiological, radiographic, and histologic endpoints.

Results

In the total study cohort, 9.1% were observed to have PBM as a histologic finding in resected lung tissue (n = 32). All but one of these patients with PBM were ever-smokers with a median of 42 pack years. Clinical COPD was diagnosed in two-thirds of patients with PBM. Comorbid gastroesophageal reflux disease (GERD) was significantly associated with PBM. All patients with PBM demonstrated radiologic and histologic evidence of emphysema. Measures of pulmonary function were not impacted by PBM. Mortality was not associated with the histologic observation of PBM. In a logistic regression model, centrilobular-ground glass opacity interstitial lung abnormality and traction bronchiectasis on the CT scan of the chest and histologic evidence of fibrosis, desquamative interstitial pneumonia and anthracosis all strongly predicted PBM in the cohort.

Conclusion

A constellation of radiologic and histologic smoking-related abnormalities predicted PBM in study cohort. This confirms a co-existence of lung tissue responses to smoking including PBM, emphysema, and fibrosis. Acknowledging the physiologically "silent" nature of small airway dysfunction on pulmonary function testing, our findings support PBM as a histologic marker of small-airway injury associated with cigarette smoking.

Hypersensitivity pneumonitis: Airway-centered pulmonary fibrosis on chest CT

BACKGROUND

To evaluate the chest CT appearance of patients with a clinicopathologic diagnosis of hypersensitivity pneumonia.

METHODS

IRB approval was obtained for a retrospective review of patients with a preoperative CT scan, a surgical pathology report from a transbronchial biopsy or wedge resection consistent with hypersensitivity pneumonitis, and a pulmonary consultation, which also supported the diagnosis. The pathology report was evaluated for granulomas, airway-centered fibrosis, microscopic honeycombing, and fibroblast foci. The medical records were reviewed for any known antigen exposure. Patients were separated into two groups; those with and without a known antigen exposure. The CT scans were assessed for distribution of fibrosis: upper lobe or lower lobe predominance, airway-centered versus peripheral distribution, three-density pattern, and honeycombing.

RESULTS

264 pathology reports included the term chronic hypersensitivity pneumonitis (CHP). Thirty-eight of the patients had a pulmonologist who gave the patient a working diagnosis of CHP. The average age of these patients was 64 years, and 21/38 were women. Seventeen of the 38 patients had at least one antigen exposure described in the medical records. All the patients had fibrosis along the airways on chest CT. Both known antigen exposure and no known antigen patients had upper and lower lung-predominant fibrosis. There were more patients with hiatal hernias in the unknown antigen group. Honeycombing was an uncommon finding.

CONCLUSION

Airway-centered fibrosis was present on chest CT in all 38 patients with CHP (100%), with or without known antigen exposure.

Diagnosis and Evaluation of Hypersensitivity Pneumonitis: CHEST Guideline and Expert Panel Report

BACKGROUND

The purpose of this analysis is to provide evidence-based and consensus-derived guidance for clinicians to improve individual diagnostic decision-making for hypersensitivity pneumonitis (HP) and decrease diagnostic practice variability.

STUDY DESIGN AND METHODS

Approved panelists developed key questions regarding the diagnosis of HP using the PICO (Population, Intervention, Comparator, Outcome) format. MEDLINE (via PubMed) and the Cochrane Library were systematically searched for relevant literature, which was supplemented by manual searches. References were screened for inclusion, and vetted evaluation tools were used to assess the quality of included studies, to extract data, and to grade the level of evidence supporting each recommendation or statement. The quality of the evidence was assessed using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) approach. Graded recommendations and ungraded consensus-based statements were drafted and voted on using a modified Delphi technique to achieve consensus. A diagnostic algorithm is provided, using supporting data from the recommendations where possible, along with expert consensus to help physicians gauge the probability of HP.

RESULTS

The systematic review of the literature based on 14 PICO questions resulted in 14 key action statements: 12 evidence-based, graded recommendations and 2 ungraded consensus-based statements. All evidence was of very low quality.

INTERPRETATION

Diagnosis of HP should employ a patient-centered approach and include a multidisciplinary assessment that incorporates the environmental and occupational exposure history and CT pattern to establish diagnostic confidence prior to considering BAL and/or lung biopsy. Criteria are presented to facilitate diagnosis of HP. Additional research is needed on the performance characteristics and generalizability of exposure assessment tools and traditional and new diagnostic tests in modifying clinical decision-making for HP, particularly among those with a provisional diagnosis.

Carbohydrate antigen 15-3 as a marker of disease severity in patients with chronic hypersensitivity pneumonitis

Objective:

Biomarkers associated with mucin 1, such as Krebs von den Lungen-6 and carbohydrate antigen (CA) 15-3, are increased in various interstitial lung diseases. Our aim was to determine whether CA 15-3 could be considered a biomarker of disease severity in patients with chronic hypersensitivity pneumonitis (cHP).

Methods:

This was a prospective observational study involving adult patients with cHP. Serum levels of CA 15-3 were measured and were correlated with variables related to disease severity and extension. HRCT scans were quantitatively analyzed using a computational platform and an image analysis tool (Computer Aided Lung Informatics for Pathology Evaluation and Rating). CA 15-3 levels were normalized by logarithmic transformation.

Results:

The sample comprised 41 patients. The mean age of the patients was 60.1 ± 11.6 years. The mean FVC in % of predicted was 70.3% ± 17.3%, and the median of the serum level of CA 15-3 was 48.1 U/mL. CA 15-3 levels inversely correlated with FVC in % of predicted (r = −0,30; p = 0,05), DLCO in % of predicted (r = −0,54; p < 0,01), and SpO₂ at the end of a 4-min step test (r = −0,59; p < 0,01), but they directly correlated with total quantitative HRCT scores (r = 0,47; p = 0,004), especially regarding ground-glass opacities (r = 0.58; p < 0,001).

Conclusions:

CA 15-3 is likely to be a biomarker of disease severity of patients with cHP, particularly regarding gas exchange abnormalities.

Histopathologic Assessment of Suspected Idiopathic Pulmonary Fibrosis: Where We Are and Where We Need to Go

CONTEXT.—

Accurate diagnosis of idiopathic pulmonary fibrosis (IPF) requires multidisciplinary diagnosis that includes clinical, radiologic, and often pathologic assessment. In 2018, the American Thoracic Society, European Respiratory Society, Japanese Respiratory Society, and the Latin American Thoracic Society (ATS/ERS/JRS/ALAT) and the Fleischner Society each published guidelines for the diagnosis of IPF, which include criteria for 4 categories of confidence of a histologic usual interstitial pneumonia (UIP) pattern.

OBJECTIVE.—

To (1) identify the role of the guidelines in pathologic assessment of UIP; (2) analyze the 4 guideline categories, including potential areas of difficulty; and (3) determine steps the Pulmonary Pathology Society and the greater pulmonary pathology community can take to improve current guideline criteria and histopathologic diagnosis of interstitial lung disease.

DATA SOURCES.—

Data were derived from the guidelines, published literature, and clinical experience.

CONCLUSIONS.—

Both guidelines provide pathologists with a tool to relay to the clinician the likelihood that a biopsy represents UIP, and serve as an adjunct, not a replacement, for traditional histologic diagnosis. There are multiple challenges with implementing the guidelines, including (1) lack of clarity on the quantity and quality of histologic findings required, (2) lack of recognition that histologic features cannot be assessed independently, and (3) lack of guidance on how pathologists should incorporate clinical and radiographic information. Current criteria for "probable UIP" and "indeterminate for UIP" hinder accurate reflection of the likelihood of IPF. These challenges highlight the need for further morphologic-based investigations in the field of pulmonary pathology.

Clinical diagnosis of patients subjected to surgical lung biopsy with a probable usual interstitial pneumonia pattern on high-resolution computed tomography

Background

Usual interstitial pneumonia can present with a probable pattern on high-resolution computed tomography (HRCT), but the probability of identifying usual interstitial pneumonia by surgical lung biopsy in such cases remains controversial. We aimed to determine the final clinical diagnosis in patients with a probable usual interstitial pneumonia pattern on HRCT who were subjected to surgical lung biopsy.

Methods

HRCT images were assessed and categorized by three radiologists, and tissue slides were evaluated by two pathologists, all of whom were blinded to the clinical findings. The final clinical diagnosis was accomplished via a multidisciplinary discussion. Patients with a single layer of honeycombing located outside of the lower lobes on HRCT were not excluded.

Results

A total of 50 patients were evaluated. The most common final clinical diagnosis was fibrotic hypersensitivity pneumonitis (38.0%) followed by idiopathic pulmonary fibrosis (24.0%), interstitial lung disease ascribed to gastroesophageal reflux disease (12.0%) and familial interstitial lung disease (10.0%). In the group without environmental exposure (n = 22), 10 patients had a final clinical diagnosis of idiopathic pulmonary fibrosis (45.5%). Irrespective of the final clinical diagnosis, by multivariate Cox analysis, patients with honeycombing, dyspnoea and fibroblastic foci on surgical lung biopsy had a high risk of death.

Conclusions

The most common disease associated with a probable usual interstitial pneumonia pattern on HRCT is fibrotic hypersensitivity pneumonitis followed by idiopathic pulmonary fibrosis and interstitial lung disease ascribed to gastroesophageal reflux disease. In patients without environmental exposure, the frequencies of usual interstitial pneumonia and a final clinical diagnosis of idiopathic pulmonary fibrosis are not sufficiently high to obviate the indications for surgical lung biopsy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-020-01339-9.

Airway-centered Interstitial Fibrosis Involving Smooth Muscle Hyperplasia with Severe Pulmonary Hypertension

In the 2013 updated classification of the American Thoracic Society/European Respiratory Society, airway-centered interstitial fibrosis (ACIF) is included as a bronchiolocentric pattern of interstitial pneumonia (IP) among idiopathic IPs. We encountered a case of severe pulmonary hypertension (PH) with chronic IP. The patient initially presented with shortness of breath and often lost consciousness due to PH, and seven years after his first visit, he ultimately died. An autopsy revealed ACIF and usual IP. In particular, the ACIF comprised non-atypical smooth muscle hyperplasia, and pulmonary hypertensive vascular degeneration was detected. This case may represent a new pathological feature of ACIF.

Pathology of Idiopathic Interstitial Pneumonias

This review discusses diagnostic pathology in idiopathic interstitial pneumonias (IIPs). Accurate understanding of basic structure of lung lobules is critical because the location of abnormalities inside the lobule is an important effector of pathology diagnosis. Depending on the method of obtaining tissue, recognition of the location may be difficult or impossible. Cryobiopsy is a new technology and its coverage of lung lobules is limited. This article discusses fundamental anatomy and approach to interstitial pneumonia. In addition, most histologic types of IIPs are covered, but the focus is on diagnosis of usual interstitial pneumonia because of its clinical importance.

Update on Rare Idiopathic Interstitial Pneumonias and Rare Histologic Patterns

CONTEXT

- In 2013, the revised American Thoracic Society and European Respiratory Society classification of idiopathic interstitial pneumonias (IIPs) described 2 rare IIPs and 2 rare histologic patterns. Because of the rarity of the disease, there is limited evidence related to the histology. Because the rare histologic patterns are provisional criteria, no unanimous consensus on histologic diagnostic criteria has yet been reached.

OBJECTIVE

- To review the histologic features for rare IIPs and rare histologic patterns, and to provide diagnostic aids and discuss the differential diagnosis.

DATA SOURCES

- Published peer-reviewed literature and the authors' personal experience.

CONCLUSIONS

- Following the publication of the international consensus classification, evidence regarding rare IIPs and rare histologic patterns has accumulated to some extent, although to date the amount remains insufficient and further evidence is required. Because the diagnosis is sometimes challenging, a multidisciplinary approach represents the gold standard in reaching an accurate diagnosis for these rare disorders.

Squawks in interstitial lung disease prevalence and causes in a cohort of one thousand patients

Squawks are lung adventitious sounds with a mix of both musical and nonmusical components heard during the inspiratory phase. Small series have described squawks in interstitial lung diseases. Hypersensitivity pneumonitis and other diseases involving small airways can result in squawks, but new interstitial lung diseases (ILDs) involving peripheral airways are being described. A retrospective analysis was performed on 1000 consecutive patients from a database of ILD of a tertiary referral center. Squawks were recorded in 49 cases (4.9%), hypersensitivity pneumonitis (23 cases), connective tissue disease (7), microaspiration (4), pleuroparenchymal fibroelastosis (4), fibrosing cryptogenic organizing pneumonia (, 3), familial ILD (2), sarcoidosis (2), idiopathic pulmonary fibrosis (IPF; 1), bronchiolitis (2), and nonspecific interstitial pneumonia (1). One patient had a final diagnosis of IPF. There was a significant association between mosaic pattern and squawks: 20 cases with squawks (40.8%) had mosaic pattern compared with 140 (14.7%) cases without squawks (x = 23.6, P < .001).Findings indicative of fibrosis were described on high-resolution chest tomography (HRCT) in 715 cases (71.5%). Squawks were more common in patients with findings indicative of fibrosis on HRCT: 45 of 715 (6.3%) compared with 4 of 285 (1.4%) of those without findings indicative of fibrosis (x = 10.46, P = .001).In conclusion, squawks are an uncommon finding on physical examination in patients with ILD, but when present suggest fibrosing ILD associated with bronchiolar involvement. However, squawks are rare in IPF.

Familial pulmonary fibrosis: a heterogeneous spectrum of presentations

Objective:

To describe the clinical, functional, and radiological features of index cases of familial pulmonary fibrosis (FPF) in Brazil.

Methods:

We evaluated 35 patients with FPF - of whom 18 (51.4%) were women - with a median age of 66.0 years (range, 35.5-89.3 years). All of the patients completed a standardized questionnaire, as well as undergoing pulmonary function tests and HRCT of the chest. In 6 cases, lung tissue samples were obtained: from surgical biopsies in 5 cases; and from an autopsy in 1 case.

Results:

A history of smoking and a history of exposure to birds or mold were reported in 45.7% and 80.0% of the cases, respectively. Cough and marked dyspnea were reported by 62.8% and 48.6% of the patients, respectively. Fine crackles were detected in 91.4% of the patients. In 4 patients, the findings were suspicious for telomere disease. The median FVC and DLCO, as percentages of the predicted values, were 64.9% (range, 48.8-105.7%) and 38.9% (range, 16.0-60.0%), respectively. Nine patients had reduced DLCO despite having normal spirometry results. Regarding HRCT, patterns typical of usual interstitial pneumonia were found in 6 patients (17.1%). In 25 cases (71.5%), the HRCT features were consistent with a diagnosis other than idiopathic pulmonary fibrosis. In 11 cases (31.4%), the radiological patterns were uncharacteristic of interstitial lung disease. Of the six lung tissue samples analyzed, four showed interstitial pneumonia with bronchiolocentric accentuation, and, on the basis of the clinical and radiological data, the corresponding patients were diagnosed with hypersensitivity pneumonitis.

Conclusions:

Patients with FPF can present with a wide variety of clinical features. Most HRCT scans of these patients exhibit patterns not typical of usual interstitial pneumonia. The family history of fibrotic lung diseases should be investigated in all patients under suspicion, regardless of their age.

Significance of bronchiolocentric fibrosis in patients with histopathological usual interstitial pneumonia

AIMS

To evaluate the clinical significance of bronchiolocentric fibrosis (BCF) in patients with a histopathological pattern of usual interstitial pneumonia (UIP).

METHODS AND RESULTS

Two hundred and fifty-two patients with pathological UIP pattern were identified. Two hundred and fifteen of these patients (215 of 252) had the multidisciplinary diagnosis of idiopathic pulmonary fibrosis (IPF). Prospectively defined clinical, radiological and pathological features (including BCF) were recorded, and peripheral blood MUC5B genotype and telomere length were measured. BCF was observed in 38% (96 of 252) of all patients and 33% (72 of 215) of IPF patients; its presence was associated with a non-IPF diagnosis on multivariate analysis (odds ratio = 3.71, 95% confidence interval = 1.68-8.19). BCF was not significantly associated with environmental exposures, gastroesophageal reflux, cigarette smoking or radiological patterns. There was no significant association of BCF with MUC5B genotype or telomere length. BCF has no significant impact on survival time.

CONCLUSIONS

Most patients with BCF and a histopathological pattern of UIP have IPF. However, this combined fibrotic pattern is associated with a non-IPF multidisciplinary diagnosis, with approximately one-quarter of these patients being diagnosed as chronic hypersensitivity pneumonia or unclassifiable interstitial fibrosis. The presence of BCF in these patients is not significantly associated with presumed clinical risk factors for bronchiolocentric involvement, radiological findings, MUC5B genotype, telomere length or survival time.

Perspectives in veterinary medicine: Description and classification of bronchiolar disorders in cats

This Perspectives in Veterinary Medicine article seeks to define, describe putative causes, and discuss key diagnostic tests for primary and secondary bronchiolar disorders to propose a classification scheme in cats with support from a literature review and case examples. The small airways (bronchioles with inner diameters <2 mm), located at the transitional zone between larger conducting airways and the pulmonary acinus, have been overlooked as major contributors to clinical syndromes of respiratory disease in cats. Because the trigger for many bronchiolar disorders is environmental and humans live in a shared environment with similar susceptibility, understanding these diseases in pet cats has relevance to One Health. Thoracic radiography, the major imaging modality used in the diagnostic evaluation of respiratory disease in cats, has low utility in detection of bronchiolar disease. Computed tomography (CT) with paired inspiratory and expiratory scans can detect pathology centered on small airways. In humans, treatment of bronchiolar disorders is not well established because of heterogeneous presentations and often late definitive diagnosis. A review of the human and veterinary medical literature will serve as the basis for a proposed classification scheme in cats. A case series of cats with CT or histopathologic evidence of bronchiolar lesions or both, either as a primary disorder or secondary to extension from large airway disease or interstitial lung disease, will be presented. Future multi‐institutional and multidisciplinary discussions among clinicians, radiologists, and pathologists will help refine and develop this classification scheme to promote early and specific recognition and optimize treatment.

Airway-centered interstitial fibrosis - an under-recognized subtype of diffuse parenchymal lung diseases

Airway centered interstitial fibrosis (ACIF) has been recently suggesed as a rare histological pattern of interstitial lung disease of variable etiology and outcome. It is characterized by fibrosis of the respiratory bronchioles and the peribronchiolar interstitium. We describe the clinical features of 13 patients (7 female, mean age 55 years) with histologically proven ACIF in 12 cases and long-term follow up. In ten patients, exogenous agents could be detected (mould n=5, wood n=2, leather exposure n=1, occupational exposure n=2). Two patients had rheumatoid arthritis and 1 patient suffered from recurrent aspiration. In three patients no associated exposure could be detected. Eight patients were never-smokers, while five were ex- smokers. At time of diagnosis patients presented with a moderate restrictive ventilation impairment and sever reduction in diffusion capacity (VC 61%, TLC 66%, DLCOc-SB 38% pred.). All patients were started on immunosuppressive therapy with steroids which were combined with azathioprine in seven and with mycophenolate mofetil in one patient. Median time of follow up was 52 months (2-127 months). Patients with ACIF due to exogenous agents or associated with RA were stable with immunosuppressive therapy. One patient with idiopathic ACIF showed a progressive deterioration within 29 months despite immunosuppression and died while on a waiting-list for lung transplantation. In our experience ACIF is a rare finding, which is relatively frequently observed in the context of hypersensitivity pneumonitis, aspiration and rheumatoid arthritis, while idiopathic ACIF was a minority. In the majority of patients, ACIF showed a favorable long-term outcome with immunosuppressive therapy. (Sarcoidosis Vasc Diffuse Lung Dis 2018; 35: 218-229).

Pathology of Chronic Hypersensitivity Pneumonitis What Is It? What Are the Diagnostic Criteria? Why Do We Care?

Context.—

Chronic hypersensitivity pneumonitis (CHP) has emerged from obscurity during the past 15 years and is now recognized as a very common form of fibrosing interstitial pneumonia but one that is frequently misdiagnosed both clinically and on surgical lung biopsy as usual interstitial pneumonia/idiopathic pulmonary fibrosis (UIP/IPF) or fibrotic nonspecific interstitial pneumonia.

Objective.—

To review the pathologic features of CHP.

Data Sources.—

Clinical, pathology, and radiology literature were used.

Conclusions.—

Upper lobe–predominant fibrosis and/or air-trapping on computed tomography scan are features of CHP but not UIP/IPF; however, radiologic separation is possible in only about 50% of cases. Morphologically, CHP sometimes mimics UIP/IPF, but CHP often shows isolated foci of peribronchiolar (centrilobular) fibrosis, frequently associated with fibroblast foci, and in CHP, fibrosis may bridge from the centrilobular region to another bronchiole, an interlobular septum, or the pleura (“bridging fibrosis”). This set of findings is uncommon in UIP/IPF. In addition, CHP may produce a picture of fibrotic nonspecific interstitial pneumonia. Although giant cells/granulomas are usually present in subacute hypersensitivity pneumonitis, they are much less frequently found in CHP, and their absence does not contradict the diagnosis. This diagnostic separation is clinically important because CHP is treated differently than UIP/IPF is (immunosuppressive agents versus antifibrotic agents); further, there are some data to suggest that removing the patient from antigen exposure improves outcome, and there is evidence that patients with CHP have a much better survival prognosis after lung transplantation than do patients with UIP/IPF. In most cases, accurate diagnosis of CHP requires consultation among clinicians, radiologists, and pathologists.

Chronic hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HSP) is a common interstitial lung disease resulting from inhalation of a large variety of antigens by susceptible individuals. The disease is best classified as acute and chronic. Chronic HSP can be fibrosing or not. Fibrotic HSP has a large differential diagnosis and has a worse prognosis. The most common etiologies for HSP are reviewed. Diagnostic criteria are proposed for both chronic forms based on exposure, lung auscultation, lung function tests, HRCT findings, bronchoalveolar lavage, and biopsies. Treatment options are limited, but lung transplantation results in greater survival in comparison to idiopathic pulmonary fibrosis. Randomized trials with new antifibrotic agents are necessary.

Diagnostic Approach to Advanced Fibrotic Interstitial Lung Disease: Bringing Together Clinical, Radiologic, and Histologic Clues

Context.—

Idiopathic pulmonary fibrosis (IPF) is a distinctive clinicopathologic entity and the most common form of progressive diffuse lung scarring in older adults. Idiopathic pulmonary fibrosis manifests histopathologically as the usual interstitial pneumonia pattern. The usual interstitial pneumonia pattern is distinguished by geographically and temporally heterogeneous fibrosis that is peripherally accentuated, often with honeycombing and traction bronchiectasis. Idiopathic pulmonary fibrosis is not the only disease that leads to end-stage lung fibrosis, however, and several other entities may also cause advanced fibrosis. Surgical lung biopsies often present a diagnostic dilemma when they show clear evidence of advanced fibrosis, but the clinical, imaging, and/or histopathologic subcharacteristics suggest something other than IPF.

Objective.—

To address this dilemma, we review several other fibrotic lung diseases, including connective tissue disease–associated interstitial lung disease, chronic hypersensitivity pneumonitis, advanced pulmonary Langerhans cell histiocytosis, end-stage pulmonary sarcoidosis, Erdheim-Chester disease, Hermansky-Pudlak syndrome, and others, detailing their clinical, radiologic, and histopathologic attributes and emphasizing similarities to and differences from IPF.

Data Sources.—

Data sources comprised published peer-reviewed literature and personal experience of the authors.

Conclusions.—

Often, clues in the lung biopsy may offer the first suggestion of a fibrotic lung disease other than IPF, and accurate classification is important for prognosis, treatment, and the development of future therapies.

Update on Pulmonary Fibrosis: Not All Fibrosis Is Created Equally

CONTEXT

Three distinct patterns of pulmonary fibrosis, including usual interstitial pneumonia, fibrotic nonspecific interstitial pneumonia, and airway-centered fibrosis, can be identified on surgical lung biopsies.

OBJECTIVES

To compare the pathologic definitions, clinical and radiographic presentations, etiologies and differential diagnoses, treatments, and prognoses of usual interstitial pneumonia, fibrotic nonspecific interstitial pneumonia, and airway-centered fibrosis patterns, and to address the challenges and controversies related to pulmonary fibrosis.

DATA SOURCES

Data were derived from published literature and clinical experience.

CONCLUSIONS

Although there may be overlap, identification of the dominant form of fibrosis in a particular case can provide a general category of disease and assist in identifying an etiology.

Screening for Helicobacter pylori in Idiopathic Pulmonary Fibrosis Lung Biopsies

BACKGROUND

Increasing evidence suggests a role of gastro-oesophageal reflux (GER) in idiopathic pulmonary fibrosis (IPF) pathogenesis. Recently, an association between serum Helicobacter pylori (HP) antibody positivity and more severe disease was described, but HP has not been directly analysed in lung tissue so far.

OBJECTIVE

To investigate the presence of HP in the lung tissue of IPF patients.

METHODS

Two tertiary interstitial lung disease care centre databases were screened for available lung biopsy material from IPF patients. Clinical and radiological data, including presence of GER and antiacid medication, were evaluated. HP-specific PCR was carried out on the IPF lung biopsy specimens.

RESULTS

A total of 39 IPF patients were included, of whom 85% were male. The patients' median age was 66 years, their vital capacity was 79% predicted, and their diffusing capacity for carbon monoxide was 53% predicted. In all, 82% of the lung biopsies were surgical and 18% transbronchial. Comorbidities were GER disease in 23% (n = 9), sleep apnoea in 13% (n = 5) and hiatal hernia in 38% of the cases (n = 15). Proton pump inhibitors were prescribed at the time of biopsy in 21% of the cases (n = 9). After a median follow-up of 25 months (range 6-69), there were 1 death, 1 lung transplantation and 8 acute exacerbations without relevant differences between the GER and non-GER subgroups. HP DNA was not detected in any of the lung tissue samples.

CONCLUSION

The fact that no HP DNA was detected in the lung tissues calls into question the proposed relevance of HP to the direct pathogenesis of IPF.