Fibrosing Bronchiolitis Evolving from Infectious or Inhalational Acute Bronchiolitis. A Reversible Lesion

Systematic Review of Systemic Corticosteroids for Treatment of Organizing Pneumonia

Introduction

Regardless corticosteroids are recommended for the treatment of organizing pneumonia there is limited evidence supporting this practice. Thus, we performed a systematic review of the literature on systemic corticosteroid treatment for organizing pneumonia.

Methods

A search was implemented in the PubMed database (Medline) for articles published in the last 20 years. Those studies with incomplete or insufficient data and case reports were excluded. We collected data including: demographics, clinical data, diagnostic procedures, aetiology, treatment regimen (drug, posology, duration, response) and evolution.

Results

A total of 135 publications were selected and finally 13 studies with 849 patients were included in the review: 12 retrospective observational studies and a single prospective observational study. Most of the patients were started on treatment with systemic corticosteroids - a total of 627 (30-100% depending on the series), but there was a great heterogeneity regarding drug, doses and duration. On those that started treatment, 226 (36%) presented a relapse of the disease during follow-up. Only one study provided information regarding treatment side-effects.

Conclusion

The findings of this systematic review show the low quality data supporting the use of corticosteroids for the treatment of organizing pneumonia. This highlights a need to undertake appropriately designed studies to investigate which is the most appropriate treatment regimen that trades off benefits and risks of prolonged corticosteroid administration.

Diagnosis of Hypersensitivity Pneumonitis: Review and Summary of American College of Chest Physicians Statement

Assessment of lung biopsies for the diagnosis of hypersensitivity pneumonitis (HP) is one of the most difficult diagnostic problems for surgical pathologists. It is a form of interstitial lung disease resulting from an immune reaction provoked by an inhaled antigen in susceptible individuals. Although this definition sounds simple, in practice, the diagnosis of HP can be challenging. To address these issues, the American College of Chest Physicians (CHEST) has recently published a guideline for the diagnosis of HP. In this review, we will explore the multidisciplinary diagnostic evaluation of HP with a focus on the pathologic features as outlined in the CHEST guidelines. The histologic criteria are divided into 4 diagnostic categories: (1) Typical nonfibrotic HP or fibrotic HP; (2) Compatible with nonfibrotic HP or fibrotic HP; (3) Indeterminate for nonfibrotic or fibrotic HP; and (4) Alternative Diagnosis. It is important to emphasize that patterns 1 to 3 do not represent discrete histologic entities or pathologic diagnoses. Rather, these categories are meant to serve as a practical guide for organizing a complex set of overlapping histologic patterns into an integrated diagnostic framework for facilitating multidisciplinary discussion. High-resolution computed tomography features are also summarized, emphasizing how the correlation of lung biopsies with computed tomography findings can help to favor the diagnosis, particularly in cases where biopsies are not typical for HP. This review highlights details of the histologic spectrum of HP as well as the utility of different types of biopsies and bronchoalveolar lavage. We also emphasize the importance of multidisciplinary discussion and the complex differential diagnosis.

Cigarette Smoke Particle-Induced Lung Injury and Iron Homeostasis

It is proposed that the mechanistic basis for non-neoplastic lung injury with cigarette smoking is a disruption of iron homeostasis in cells after exposure to cigarette smoke particle (CSP). Following the complexation and sequestration of intracellular iron by CSP, the host response (eg, inflammation, mucus production, and fibrosis) attempts to reverse a functional metal deficiency. Clinical manifestations of this response can present as respiratory bronchiolitis, desquamative interstitial pneumonitis, pulmonary Langerhans’ cell histiocytosis, asthma, pulmonary hypertension, chronic bronchitis, and pulmonary fibrosis. If the response is unsuccessful, the functional deficiency of iron progresses to irreversible cell death evident in emphysema and bronchiectasis. The subsequent clinical and pathological presentation is a continuum of lung injuries, which overlap and coexist with one another. Designating these non-neoplastic lung injuries after smoking as distinct disease processes fails to recognize shared relationships to each other and ultimately to CSP, as well as the common mechanistic pathway (ie, disruption of iron homeostasis).

Inhalational Constrictive Bronchiolitis: The Evolution of our Understanding of this Disease

The case definition of inhalational constrictive bronchiolitis (CB) has changed over the generations. We identify changes in the description of this illness over time associated with different exposures and present the natural history of CB in a case attributed to military burn pit exposure. The initial descriptions of this disease began with nitric acid spills and silage exposures. In these events, there was an acute exposure, typically a short-term resolution of the adverse respiratory events, and then a progression, leading to disability or a respiratory death. The life-saving role of corticosteroid therapy in this situation was recognized. War gas exposures of World War I and then Saddam Hussein's use of sulfur mustard gas in the Iran-Iraq War followed. More recently the findings associated with diacetyl exposure in commercial popcorn workers remained consistent with previously described presentations, but then the clinical presentation in troops returning from deployment to Southwest Asia was very different, yet with the same histologic findings. We recognize unreconciled disparities in the clinical, physiologic, and imaging presentation in those with inhalational bronchiolitis and acknowledge this as perhaps one of the difficult diagnoses in respiratory medicine.

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.

Occupational Bronchiolitis: An Update

Occupational bronchiolitis is characterized by inflammation of the small airways, and represents a heterogeneous set of lung conditions that can occur following a range of inhalation exposures related to work. The most common clinical presentation includes insidious onset of exertional dyspnea and cough. Multiple reports in recent years have drawn attention to previously unrecognized risk factors for occupational bronchiolitis following exposures in several settings. Both current and past occupational exposures, including prior military deployment-related exposures, should be considered in patients undergoing evaluation for unexplained dyspnea. Diagnostic testing for potential bronchiolitis should include a thorough assessment of the small airways.

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.

Persistent effects of chlorine inhalation on respiratory health

Chlorine gas is a toxic respiratory irritant that is considered a chemical threat agent because of the potential for release in industrial accidents or terrorist attacks. Chlorine inhalation damages the respiratory tract, including the airways and distal lung, and can result in acute lung injury. Some individuals exposed to chlorine experience a full recovery from acute injury, whereas others develop persistent adverse effects, such as respiratory symptoms, inflammation, and lung-function decrements. In animal models, chlorine can produce persistent inflammation, remodeling, and obstruction in large or small airways, depending on species. Airways with pseudostratified epithelia are repaired efficiently, with surviving basal epithelial cells serving as progenitor cells that repopulate the complement of differentiated cell types. Distal airways lacking basal cells are repaired less efficiently, leading to chronic inflammation and fibrosis at these sites. Persistent chlorine-induced airway disease in humans is treated with asthma medication to relieve symptoms. However, such treatment does not ameliorate the underlying disease pathogenesis, so treatments that are more effective at preventing initial development of airway disease after irritant gas exposure and at reversing established disease are needed.