BACKGROUND: Hypersensitivity pneumonitis (HP) is a complex and heterogenous interstitial lung disease (ILD) that occurs in susceptible individuals due to certain inhaled antigens. Fibrotic-HP is a major underlying disease of progressive pulmonary fibrosis. Therefore, in addition to the radiological features of HP, quantitatively measuring fibrosis is important to evaluate disease severity and progression. The present study aimed to compare three-dimensional computed tomography (3D-CT)-derived lung volumes (LVs) of patients with HP and determine its association with mortality risk.
METHODS: In this retrospective and multicenter cohort study, 126 patients diagnosed with HP (fibrotic, n = 72 and non-fibrotic, n = 54) with a confidence level higher than moderate were enrolled. Each lobe LV was measured using 3D-CT at the time of diagnosis and standardized using predicted forced vital capacity. The 3D-CT LV was compared with those of 42 controls and 140 patients with idiopathic pulmonary fibrosis (IPF).
RESULTS: Compared to patients with fibrotic-HP, the standardized total LV was significantly higher in controls and patients with non-fibrotic-HP and was similar in patients with IPF. Longitudinal analyses demonstrated that approximately half of the patients with fibrotic-HP had an annual decrease in total LV. Decreased total and lower-lobe LVs were associated with shorter survival, and were independently associated with mortality together with ongoing exposure to inciting antigens. A composite model consisting of ongoing exposure to inciting antigens and total or lower-lobe LV successfully classified mortality risk into three groups.
CONCLUSIONS: Quantitatively measuring standardized LV can help determine disease severity, progression, and mortality risk in patients with fibrotic-HP.

BACKGROUND: The importance of multidisciplinary discussion (MDD) for diagnosing interstitial lung disease (ILD) is emphasized by several international guidelines. While initial diagnoses are often provisional and require periodic re-evaluation, there is a lack of literature regarding the role of follow-up MDD in clinical practice.
METHODS: From September 2020 to January 2022, patients underwent an initial MDD (MDD1) based on clinical, radiological, and pathological evaluations. Each diagnosis was assigned a confidence level. One year later, a second MDD (MDD2) was conducted for re-evaluation, based on subsequent clinical and radiological information. Changes in diagnosis and confidence levels between MDD1 and MDD2 were assessed.
RESULTS: Among 52 patients enrolled in both MDDs, the diagnosis for 13 (25%) was revised at MDD2. Of these, 10 patients were initially diagnosed with unclassifiable ILD, and 3 received a low confidence diagnosis of either idiopathic pulmonary fibrosis or idiopathic nonspecific interstitial pneumonia. The most common diagnostic revision was due to the deterioration after antigen exposure or improvement after antigen avoidance, which resulted in a revised diagnosis of HP at MDD2.
CONCLUSIONS: Our findings underscore the importance of periodic reassessment of MDD to improve the accuracy of ILD diagnosis. This study highlights the significance of longitudinal clinical and radiological evaluation for diagnostic revision, even in situations when rebiopsy is not feasible.

OBJECTIVE: Transbronchial cryobiopsies are increasingly used for the diagnosis of interstitial lung disease (ILD), but there is a lack of published information on the features of specific ILD in cryobiopsies. Here we attempt to provide pathological guidelines for separating usual interstitial pneumonia (UIP) of idiopathic pulmonary fibrosis (IPF), fibrotic hypersensitivity pneumonitis (FHP) and connective tissue disease-associated ILD (CTD-ILD) in cryobiopsies.
METHODS: We examined 120 cryobiopsies from patients with multidisciplinary discussion (MDD)-established CTD-ILD and compared them to a prior series of 121 biopsies from patients with MDD-established IPF or FHP.
RESULTS: A non-specific interstitial pneumonia (NSIP) pattern alone was seen in 36 of 120 (30%) CTD-ILD, three of 83 (3.6%) FHP and two of 38 (5.2%) IPF cases, statistically favouring a diagnosis of CTD-ILD. The combination of NSIP + OP was present in 29 of 120 (24%) CTD-ILD, two of 83 (2.4%) FHP and none of 38 (0%) IPF cases, favouring a diagnosis of CTD-ILD. A UIP pattern, defined as fibroblast foci plus any of patchy old fibrosis/fibrosis with architectural distortion/honeycombing, was identified in 28 of 120 (23%) CTD-ILD, 45 of 83 (54%) FHP and 27 of 38 (71%) IPF cases and supported a diagnosis of FHP or IPF. The number of lymphoid aggregates/mm2 and fibroblast foci/mm2 was not different in IPF, CTD-ILD or FHP cases with a UIP pattern. Interstitial giant cells supported a diagnosis of FHP or CTD-ILD over IPF, but were infrequent.
CONCLUSIONS: In the correct clinical/radiological context the pathological findings of NSIP, and particularly NSIP plus OP, favour a diagnosis of CTD-ILD in a cryobiopsy, but CTD-ILD with a UIP pattern, FHP with a UIP pattern and IPF generally cannot be distinguished.

Occupational lung disease remains one of the most common work-related illnesses and accounts for most deaths from occupational illness. Occupational lung diseases often have delayed manifestation over decades and nonspecific clinical presentations, making it challenging for clinicians to promptly identify the disease and implement preventive measures. Radiologists play a crucial role in identifying and diagnosing occupational lung diseases, allowing for removal of the exposure and early medical intervention. In this review, we share our clinical and radiologic approach to diagnosing occupational lung disease and its subtypes. A collection of sample cases of occupational lung diseases commonly encountered in the modern era at a large Canadian university hospital is included to facilitate understanding. This review will provide radiologists with valuable insights into recognizing and diagnosing occupational lung diseases.

We report a 60-year-old man with humidifier lung showing diffusely distributed centrilobular micronodules and branching opacities on chest computed tomography (CT). Fever and dyspnea occurred 2 months after using an ultrasonic humidifier. KL-6 and SP-D were within normal ranges. Bronchoalveolar lavage showed elevated lymphocytes (53 %) and histological findings of transbronchial lung biopsy demonstrated organizing pneumonia. His condition improved after cessation of the humidifier. A provocation test exhibited a positive response to the humidifier. Humidifier lung should be considered as a differential diagnosis in patients with these CT findings. Detailed clinical, pathological and microbiological examinations are needed to exclude other diseases.

Purpose To compare the diagnostic performance of the American Thoracic Society, Japanese Respiratory Society, and Asociación Latinoamericana del Tórax (ATS/JRS/ALAT) versus the American College of Chest Physicians (ACCP) imaging classifications for hypersensitivity pneumonitis (HP). Materials and Methods Patients in the institutional review board-approved Interstitial Lung Disease (ILD) registry referred for multidisciplinary discussion (MDD) at the authors\' institution (January 1, 2006-April 1, 2021) were included in this retrospective study when ILD was diagnosed at MDD. MDD diagnoses included HP, connective tissue disease-ILD, and idiopathic pulmonary fibrosis. Retrospective review of thin-section CT images was performed in consensus by two cardiothoracic radiologists blinded to the diagnosis. Diagnostic patterns were determined for thin-section CT images using both classifications. Discordance rates were determined. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were assessed using MDD diagnosis as the reference standard. Results A total of 297 patients were included in the study: 200 (67%) with HP, 49 (16%) with connective tissue disease-ILD, and 48 (16%) with idiopathic pulmonary fibrosis at MDD. The discordance rate between the two classifications was 21%. Assuming low HP prevalence (10%), ATS/JRS/ALAT classification outperformed ACCP classification, with greater accuracy (92.3% vs 87.6%) and greater positive predictive value (60.7% vs 42.9%). Assuming high prevalence (50%), accuracy and negative predictive value were superior using ACCP classification (81.7% vs 79.7% and 77.7% vs 72.6%, respectively), and positive predictive value was superior using ATS/JRS/ALAT classification (93.3% vs 87.1%). Conclusion Accuracy of the ATS/JRS/ALAT and ACCP HP classifications was greater in settings with low and high HP prevalence, respectively. Diagnostic performance of both classifications was discordant in a minority of cases. Keywords: CT, Thorax, Hypersensitivity Pneumonitis, Interstitial Lung Disease Supplemental material is available for this article. © RSNA, 2024.

A 50-year-old man was diagnosed with hypersensitivity pneumonitis caused by the environment of his bar owing to worsening symptoms, laboratory test results, and computed tomography images after an environmental inhalation challenge test. His hypersensitivity pneumonitis exacerbated despite receiving prednisolone 20 mg/day. The patient underwent allogeneic hematopoietic stem cell transplantation (HSCT) from a human leukocyte antigen-matched unrelated donor for myelodysplastic syndrome. No exacerbation of hypersensitivity pneumonitis was observed after HSCT. An environmental inhalation challenge test involving exposure to his bar confirmed the remission of hypersensitivity pneumonitis after HSCT. This case demonstrates that hypersensitivity pneumonitis can be remitted by HSCT.

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.
Гиперчувствительный пневмонит (ГП) — одно из самых распространенных интерстициальных заболеваний легких, проявления которого многообразны, а диагностика сложна и требует мультидисциплинарного подхода. ГП — это иммунологически обусловленное заболевание в ответ на ингаляцию антигенов. При ГП поражаются преимущественно терминальные бронхиолы с развитием интерстициального воспаления и/или фиброза, наличием ненекротических гранулем в межальвеолярных перегородках, стенках бронхиол и перибронхиолярно. В статье приведена гистологическая картина нефиброзного и фиброзного вариантов заболевания. Четкие диагностические признаки сформулированы на основании опубликованных международных рекомендаций и собственного опыта авторов.

The American Thoracic Society/European Respiratory Society/Japanese Respiratory Society/Asociación Latinoamericana de Tórax 2018 clinical practice guideline and 2022 update provide recommendations to define and diagnose idiopathic pulmonary fibrosis (IPF) in patients with newly diagnosed interstitial lung disease. The guideline emphasizes recognition of usual interstitial pneumonia (UIP) and probable UIP patterns of fibrosis on high-resolution CT, which can obviate the need for surgical lung biopsy and allow timely initiation of antifibrotic pharmacotherapy citing a high correlation with UIP on histopathology. This article reviews the recent 2022 IPF clinical practice guideline with a focus on the imaging updates.

BACKGROUND: Organic dust is associated with hypersensitivity pneumonitis, and associations with other types of interstitial lung disease (ILD) have been suggested. We examined the association between occupational organic dust exposure and hypersensitivity pneumonitis and other ILDs in a cohort study.
METHODS: The study population included all residents of Denmark born in 1956 or later with at least 1 year of gainful employment since 1976. Incident cases of hypersensitivity pneumonitis and other ILDs were identified in the Danish National Patient Register 1994-2015. Job exposure matrices were used to assign individual annual levels of exposure to organic dust, endotoxin and wood dust from 1976 to 2015. We analysed exposure-response relations by different exposure metrics using a discrete-time hazard model.
RESULTS: For organic dust, we observed increasing risk with increasing cumulative exposure with incidence rate ratios (IRR) per 10 unit-years of 1.19 (95% CI 1.12 to 1.27) for hypersensitivity pneumonitis and 1.04 (95% CI 1.02 to 1.06) for other ILDs. We found increasing risk with increasing cumulative endotoxin exposure for hypersensitivity pneumonitis and other ILDs with IRRs per 5000 endotoxin units/m3-years of 1.55 (95% CI 1.38 to 1.73) and 1.09 (95% CI 1.00 to 1.19), respectively. For both exposures, risk also increased with increasing duration of exposure and recent exposure. No increased risks were observed for wood dust exposure.
CONCLUSIONS: Exposure-response relations were observed between organic dust and endotoxin exposure and hypersensitivity pneumonitis and other ILDs, with lower risk estimates for the latter. The findings indicate that organic dust should be considered a possible cause of any ILD.
BACKGROUND: j.no.: 1-16-02-196-17.