Hypersensitivity pneumonitis: new concepts and classifications

Notch Signaling Is Associated with Pulmonary Fibrosis in Patients with Pigeon Breeder's Lung by Regulating Oxidative Stress

This study explored the molecular mechanism underlying the association of Notch signaling and oxidative stress with the occurrence of pulmonary fibrosis in patients with pigeon breeder's lung (PBL). Rat models of fibrotic PBL were constructed with freeze-dried protein powder, and the animals were divided into the control (intratracheal instillation of normal saline; n = 9), M (PBL model; intratracheal instillation of freeze-dried protein powder; n = 9), and M + D (PBL+ the Notch inhibitor DAPT; n = 9) groups. Immunohistochemistry was employed to observe the protein levels of pathway factors and α-SMA, and the levels of ROS, GSH-PX, SOD, and MDA were observed using ELISA. To verify the results of the animal experiment, cytological models were constructed. The M group and the M + D group had significantly increased α-SMA levels (P < 0.05). Although both groups had significantly higher key protein levels in the Notch channel, the M + D group had significantly lower levels relative to the M group (P < 0.05). Oxidative stress products were examined, and the levels of MDA and ROS were significantly increased, while those of GSH-PX and SOD were significantly decreased in the M and M + D groups as compared to the control, but the M group and the M + D group significantly differed (P <  0.05). These findings were further validated by the cytological experiment. Notch signaling is associated with pulmonary fibrosis in PBL by regulating cellular oxidative stress, and inhibiting this pathway can slow down pulmonary fibrosis progression.

Relationship between nailfold capillaroscopy findings and the etiology and prognosis of interstitial lung disease

OBJECTIVES

Connective tissue-associated interstitial lung diseases (CTD-ILD) are believed to be caused by microvascular damage. The objective of this study was to assess the nailfold capillaroscopy (NFC) pattern in patients diagnosed with both CTD-ILD and non-CTD-ILD to identify microvascular changes and determine the relation between capillaroscopic parameters, clinical variables, and disease-related measurements.

PATIENTS AND METHODS

This cross-sectional study included 95 patients with interstitial lung disease who applied to our Rheumatology and Chest Clinics between September 2021 and July 2023. The patients were divided into two groups based on their diagnosis: non-CTD-ILD (group 1) and CTD-ILD (group 2). Nailfold capillaroscopy was performed.

RESULTS

Ninety-five patients, 49 (51% female, mean age 62.31 ± 11.027 years) in group 1 and 46 (69.6% female, mean age 62.09 ± 10.887 years) in group 2, were included in the study. Abnormal capillary morphologies were both detected in the CTD-ILD group and the non-CTD-ILD groups. In patients with a usual interstitial pneumonia (UIP) pattern on chest computed tomography (CT), tortuosity was higher than in patients with non-specific interstitial pneumonia (NSIP) (P = 0.041), and the proportion of tortuosity increased significantly as the duration of the disease increased (P = 0.016).

CONCLUSION

Our study highlights capillaroscopic abnormalities alone may not be sufficient to differentiate CTD-ILD (other than systemic sclerosis) from non-CTD-ILD. The presence of NFC abnormalities in non-CTD-ILD may suggest that fibrotic lung disease could potentially play a role in the deterioration of the microvascular structure or abnormal angiogenesis. Our study demonstrated that a multidisciplinary approach, incorporating clinical, morphological, pathological, and serological evaluations, is necessary for interpreting ILD. Key Points • Capillaroscopic abnormalities can also be seen in non-CTD-ILD. • Capillaroscopy findings do not distinguish the non-Ssc etiology of ILD. • Nailfold capillaroscopy may have the potential to serve as a useful tool in predicting prognosis and monitoring the disease progression in patients with idiopathic pulmonary fibrosis (IPF).

The Role of Lung Microbiome in Fibrotic Interstitial Lung Disease-A Systematic Review

Interstitial Lung Disease (ILD) involves lung disorders marked by chronic inflammation and fibrosis. ILDs include pathologies like idiopathic pulmonary fibrosis (IPF), connective tissue disease-associated ILD (CTD-ILD), hypersensitivity pneumonitis (HP) or sarcoidosis. Existing data covers pathogenesis, diagnosis (especially using high-resolution computed tomography), and treatments like antifibrotic agents. Despite progress, ILD diagnosis and management remains challenging with significant morbidity and mortality. Recent focus is on Progressive Fibrosing ILD (PF-ILD), characterized by worsening symptoms and fibrosis on HRCT. Prevalence is around 30%, excluding IPF, with a poor prognosis. Early diagnosis is crucial for optimizing outcomes in PF-ILD individuals. The lung microbiome comprises all the microorganisms that are in the respiratory tract. Relatively recent research try to evaluate its role in respiratory disease. Healthy lungs have a diverse microbial community. An imbalance in bacterial composition, changes in bacterial metabolic activities, or changes in bacterial distribution within the lung termed dysbiosis is linked to conditions like COPD, asthma and ILDs. We conducted a systematic review of three important scientific data base using a focused search strategy to see how the lung microbiome is involved in the progression of ILDs. Results showed that some differences in the composition and quality of the lung microbiome exist in ILDs that show progressive fibrosing phenotype. The results seem to suggest that the lung microbiota could be involved in ILD progression, but more studies showing its exact pathophysiological mechanisms are needed.

MMP14high macrophages orchestrate progressive pulmonary fibrosis in SR-Ag-induced hypersensitivity pneumonitis

Fibrotic hypersensitivity pneumonitis (FHP) is a fatal interstitial pulmonary disease with limited treatment options. Lung macrophages are a heterogeneous cell population that exhibit distinct subsets with divergent functions, playing pivotal roles in the progression of pulmonary fibrosis. However, the specific macrophage subpopulations and underlying mechanisms involved in the disease remain largely unexplored. In this study, a decision tree model showed that matrix metalloproteinase-14 (MMP14) had higher scores for important features in the up-regulated genes in macrophages from mice exposed to the Saccharopolyspora rectivirgula antigen (SR-Ag). Using single-cell RNA sequencing (scRNA-seq) analysis of hypersensitivity pneumonitis (HP) mice profiles, we identified MMP14high macrophage subcluster with a predominant M2 phenotype that exhibited higher activity in promoting fibroblast-to myofibroblast transition (FMT). We demonstrated that suppressing toll-like receptor 2 (TLR2) and nuclear factor kappa-B (NF-κB) could attenuate MMP14 expression and exosome secretion in macrophages stimulation with SR-Ag. The exosomes derived from MMP14-overexpressing macrophages were found to be more effective in regulating the transition of fibroblasts through exosomal MMP14. Importantly, it was observed that the transfer of MMP14-overexpressing macrophages into mice promoted lung inflammation and fibrosis induced by SR-Ag. NSC-405020 binding to the hemopexin domain (PEX) of MMP-14 ameliorated lung inflammation and fibrosis induced by SR-Ag in mice. Thus, MMP14-overexpressing macrophages may be an important mechanism contributing to the exacerbation of allergic reactions. Our results indicated that MMP14 in macrophages has the potential to be a therapeutic target for HP.

The Unveiled Triad: Clinical, Radiological and Pathological Insights into Hypersensitivity Pneumonitis

Hypersensitivity pneumonitis (HP) is a diffuse parenchymal lung disease (DLPD) characterized by complex interstitial lung damage with polymorphic and protean inflammatory aspects affecting lung tissue targets including small airways, the interstitium, alveolar compartments and vascular structures. HP shares clinical and often radiological features with other lung diseases in acute or chronic forms. In its natural temporal evolution, if specific therapy is not initiated promptly, HP leads to progressive fibrotic damage with reduced lung volumes and impaired gas exchange. The prevalence of HP varies considerably worldwide, influenced by factors like imprecise disease classification, diagnostic method limitations for obtaining a confident diagnosis, diagnostic limitations in the correct processing of high-resolution computed tomography (HRCT) radiological parameters, unreliable medical history, diverse geographical conditions, heterogeneous agricultural and industrial practices and occasionally ineffective individual protections regarding occupational exposures and host risk factors. The aim of this review is to present an accurate and detailed 360-degree analysis of HP considering HRCT patterns and the role of the broncho-alveolar lavage (BAL), without neglecting biopsy and anatomopathological aspects and future technological developments that could make the diagnosis of this disease less challenging.

Noninfectious Granulomatous Lung Disease: Radiological Findings and Differential Diagnosis

Granulomatous lung diseases (GLDs) are a heterogeneous group of pathological entities that can have different clinical presentations and outcomes. Granulomas are histologically defined as focal aggregations of activated macrophages, Langerhans cells, and lymphocytes, and may form in the lungs when the immune system cannot eliminate a foreign antigen and attempts to barricade it. The diagnosis includes clinical evaluation, laboratory testing, and radiological imaging, which especially consists of high-resolution computed tomography. bronchoalveolar lavage, transbronchial needle aspiration or cryobiopsy, positron emission tomography, while genetic evaluation can improve the diagnostic accuracy. Differential diagnosis is challenging due to the numerous different imaging appearances with which GLDs may manifest. Indeed, GLDs include both infectious and noninfectious, and necrotizing and non-necrotizing granulomatous diseases and the imaging appearance of some GLDs may mimic malignancy, leading to confirmatory biopsy. The purposes of our review are to report the different noninfectious granulomatous entities and to show their various imaging features to help radiologists recognize them properly and make an accurate differential diagnosis.

[Morphology of hypersensitivity pneumonitis]

Hypersensitivity pneumonitis (HP) is one of the most common interstitial lung diseases, the manifestations of which are diverse, and the diagnosis is complex and requires a multidisciplinary approach. HP is an immunologically determined disease in response to inhaled antigens. The main feature of the disease is terminal bronchiole's involvement accompanied by interstitial inflammation and/or fibrosis together with the presence of non-necrotizing granulomas in the interalveolar septa and bronchioles. The article presents the histological features of non-fibrous and fibrotic variants of the disease. Well-defined diagnostic criteria were formulated on the basis of published international recommendations and the authors' own experience.

Pathologic Criteria for the Diagnosis of Usual Interstitial Pneumonia vs Fibrotic Hypersensitivity Pneumonitis in Transbronchial Cryobiopsies

Transbronchial cryobiopsy (TBCB) is increasingly used for the diagnosis of fibrosing interstitial pneumonias, but there are few detailed descriptions of the pathologic findings in such cases. It has been proposed that a combination of patchy fibrosis and fibroblast foci with an absence of alternative features is diagnostic of usual interstitial pneumonia (UIP; ie, idiopathic pulmonary fibrosis [IPF]) in TBCB. In this study, we reviewed 121 TBCB in which a diagnosis of fibrotic hypersensitivity pneumonitis (FHP; n = 83) or IPF (n = 38) was made by multidisciplinary discussion and evaluated a range of pathologic features. Patchy fibrosis was found in 65 of 83 (78%) biopsies from FHP and 32of 38 (84%) biopsies from UIP/IPF cases. Fibroblast foci were present in 47 of 83 (57%) FHP and 27 of 38 (71%) UIP/IPF cases. Fibroblast foci/patchy fibrosis combined did not favor either diagnosis. Architectural distortion was seen in 54 of 83 (65%) FHP and 32 of 38 (84%) UIP/IPF cases (odds ratio [OR] for FHP, 0.35; P = .036) and honeycombing in 18 of 83 (22%) and 17 of 38 (45%), respectively (OR, 0.37; P = .014). Airspace giant cells/granulomas were present in 13 of 83 (20%) FHP and 1 of 38 (2.6%) UIP/IPF cases (OR for FHP, 6.87; P = .068), and interstitial giant cells/granulomas in 20 of 83 (24%) FHP and 0 of 38 (0%) UIP/IPF (OR, 6.7 x 106; P = .000). We conclude that patchy fibrosis plus fibroblast foci can be found in TBCB from both FHP and UIP/IPF. The complete absence of architectural distortion/honeycombing favors a diagnosis of FHP, as does the presence of airspace or interstitial giant cells/granulomas, but these measures are insensitive, and many cases of FHP cannot be separated from UIP/IPF on TBCB.

Imaging Plays a Key Role in the Diagnosis and Control of the Treatment of Bone Sarcoidosis

Sarcoidosis is a multisystem granulomatous disease of unknown origin. The most frequent localizations are thoracic lymph nodes and/or parenchymal lung disease, nevertheless any other organ may be involved. Musculoskeletal sarcoidosis, previously considered a rare manifestation of the disease, is presently recognized with increasing frequency, due to the development of modern imaging modalities. The classical X-ray sign of bone sarcoidosis is the image of lace in the phalanges of the hands. Most other locations present with atypical radiological images. Therefore, they may mimic metastatic neoplastic disease, especially when they are the first sign of sarcoidosis not previously recognized. On such occasions, none of the imaging methods will give the correct diagnosis, histopathological verification, monitoring of lesions or clinical data in a patient with confirmed sarcoidosis are indicated. The article summarizes the current status of knowledge concerning the recognition and therapy of bone sarcoidosis. In addition, an illustrative case of patient with bone and bone marrow sarcoidosis is presented.

Diagnostic yield and safety of transbronchial lung cryobiopsy for diffuse parenchymal lung diseases diagnosis: Comparison between 1.7-mm and 1.9-mm probes

PURPOSE OF THE RESEARCH

transbronchial lung cryobiopsy has been recently accepted as a valid and less invasive alternative to surgical lung biopsy. The purpose of this randomized controlled study was to evaluate, for the first time, the quality and safety of biopsy specimens obtained by using the new disposable 1.7-mm cryoprobe compared with the standard re-usable 1.9 mm cryoprobe in the diagnosis of diffuse parenchymal lung diseases.

METHODS

60 consecutive patients were prospectively enrolled and randomly assigned to two different groups: 1.9 mm (group A) and 1.7 mm (group B); primary endpoints were pathological and multidisciplinary diagnostic yield, sample size and complication rate.

PRINCIPAL RESULTS

the pathological diagnostic yield of cryobiopsy was 100% in group A and 93.3% in group B (p = 0.718); cryobiopsy median diameter was 6.8 mm in group A and 6.7 mm in group B (p = 0,5241). Pneumothorax occurred in 9 patients in group A and 10 in group B (p = 0.951); mild-to-moderate bleeding in 7 cases and 9 cases in group A and B respectively (p = 0.559). No death or severe adverse events were observed.

CONCLUSIONS

there was no statistically significant difference between the two groups, regarding diagnostic yield, adverse events and sampling adequacy.

The Role of Pulmonary Surfactant Phospholipids in Fibrotic Lung Diseases

Diffuse parenchymal lung diseases (DPLD) or Interstitial lung diseases (ILD) are a heterogeneous group of lung conditions with common characteristics that can progress to fibrosis. Within this group of pneumonias, idiopathic pulmonary fibrosis (IPF) is considered the most common. This disease has no known cause, is devastating and has no cure. Chronic lesion of alveolar type II (ATII) cells represents a key mechanism for the development of IPF. ATII cells are specialized in the biosynthesis and secretion of pulmonary surfactant (PS), a lipid-protein complex that reduces surface tension and minimizes breathing effort. Some differences in PS composition have been reported between patients with idiopathic pulmonary disease and healthy individuals, especially regarding some specific proteins in the PS; however, few reports have been conducted on the lipid components. This review focuses on the mechanisms by which phospholipids (PLs) could be involved in the development of the fibroproliferative response.

Prognostic Predictive Characteristics in Patients With Fibrosing Interstitial Lung Disease: A Retrospective Cohort Study

Background: Limited data are available regarding the entire spectrum of interstitial lung disease with a progressive fibrosing feature. We investigated the prevalence and prognostic predictive characteristics in patients with PF-ILD.

Methods: This retrospective cohort study included patients with fibrosing ILD who were investigated between 1 January 2015 and 30 April 2021. We recorded clinical features and outcomes to identify the possible risk factors for fibrosing progression as well as mortality.

Results: Of the 579 patients with fibrosing ILD, 227 (39.21%) met the criteria for progression. Clubbing of fingers [odds ratio (OR) 1.52, 95% confidence interval (CI) 1.03 to 2.24, p = 0.035] and a high-resolution computed tomography (HRCT)-documented usual interstitial pneumonia (UIP)-like fibrotic pattern (OR 1.95, 95% CI 1.33 to 2.86, p = 0.001) were risk factors for fibrosis progression. The mortality was worse in patients with PF with hypoxemia [hazard ratio (HR) 2.08, 95% CI 1.31 to 3.32, p = 0.002], in those with baseline diffusion capacity of the lung for carbon monoxide (DLCO) % predicted &lt;50% (HR 2.25, 95% CI 1.45 to 3.50, p &lt; 0.001), or in those with UIP-like fibrotic pattern (HR 1.68, 95% CI 1.04 to 2.71, p &lt; 0.001).

Conclusion: Clubbing of fingers and an HRCT-documented UIP-like fibrotic pattern were more likely to be associated with progressive fibrosing with varied prevalence based on the specific diagnosis. Among patients with progressive fibrosing, those with hypoxemia, lower baseline DLCO% predicted, or UIP-like fibrotic pattern showed poor mortality.

Usual interstitial pneumonia: a clinically significant pattern, but not the final word

Usual interstitial pneumonia (UIP) is a concept that is deeply entrenched in clinical practice and the prognostic significance of UIP is well established, but the field continues to suffer from the lack of a true gold standard for diagnosing fibrotic interstitial lung disease (ILD). The meaning and usage of UIP have shifted over time and this term is prone to misinterpretation and poor diagnostic agreement. For pathologists, it is worth reflecting on the limitations of UIP and our true role in the care of patients with ILD, a controversial topic explored in two point-counterpoint editorials published simultaneously in this journal. Current diagnostic guidelines are ambiguous and difficult to apply in clinical practice. Further complicating matters for the pathologist is the paradigm shift that occurred with the advent of anti-fibrotic agents, necessitating increased focus on the most likely etiology of fibrosis rather than simply the pattern of fibrosis when pulmonologists select appropriate therapy. Despite the wealth of information locked in tissue samples that could provide novel insights into fibrotic ILDs, pulmonologists increasingly shy away from obtaining biopsies, likely because pathologists no longer provide sufficient value to offset the risks of a biopsy procedure, and pathologic assessment is insufficiently reliable to meaningfully inform therapeutic decisionmaking. To increase the value of biopsies, pathologists must first recognize the problems with UIP as a diagnostic term. Second, pathologists must realize that the primary goal of a biopsy is to determine the most likely etiology to target with therapy, requiring a shift in diagnostic focus. Third, pathologists must devise and validate new classifications and criteria that are evidence-based, biologically relevant, easy to use, and predictive of outcome and treatment response. Only after the limitations of UIP are understood will pathologists provide maximum diagnostic value from biopsies to clinicians today and advance the field forward.