Hypersensitivity Pneumonitis: A Pictorial Review Based on the New ATS/JRS/ALAT Clinical Practice Guideline for Radiologists and Pulmonologists

Insights on immune profile, pathogenesis and differential diagnosis of hypersensitivity pneumonitis and pulmonary sarcoidosis-A holistic review and bibliometric analysis

Hypersensitivity pneumonitis (HP) and sarcoidosis are granulomatous interstitial lung diseases with overlapping clinical and immunological features, posing diagnostic and therapeutic challenges. This review offers a comprehensive assessment of their immune mechanisms, etiology, and pathogenesis. HP is predominantly triggered by exposure to environmental antigens, while sarcoidosis involves an exaggerated immune response to elusive antigens. Both diseases are driven by Th1 and Th17 pathways, regulatory T-cell dysfunction, and cytokine-mediated granuloma formation. Emerging diagnostic and prognostic biomarkers, such as KL-6, GDF15, PD-1, TIGIT, and genetic regulators including m6A and m5C modifications, provide valuable insights for disease stratification. Incorporating findings from a total of 38 studies (HP: n = 13; sarcoidosis: n = 25) published in the last 5 years, this review highlights key immune regulatory mechanisms, identifies critical research gaps, and provides directions for improving differential diagnosis. Addressing these gaps through multi-omics integration, computational tools, and interdisciplinary collaboration holds significant potential for refining diagnostic accuracy, advancing therapeutic strategies, and improving patient outcomes in both HP and sarcoidosis.

Aspergillus IgG antibody testing in the diagnosis of hypersensitivity pneumonitis: A scoping review

BackgroundDiagnosis of hypersensitivity pneumonitis (HP) or extrinsic allergic alveolitis requires a combination of tests with antibody testing playing a supportive role to identify exposures.ObjectivesWe conducted a scoping review on Aspergillus antibody testing in Aspergillus-related HP to identify the utility and diagnostic cutoffs proposed in the literature. We compared these cutoffs with studies of chronic pulmonary aspergillosis (CPA) and manufacturers' cutoffs.Eligibility criteriaOnly studies addressing the diagnostic value of Aspergillus IgG or precipitins for HP were included. Separately papers defining cutoffs for CPA were tabulated.Sources of evidencePublished papers were identified in literature searches in Embase, Web of Science, and Medline.ResultsWe identified 414 papers, of which 12 were included, all published between 1965 and 2005. Occupational HP linked to Aspergillus spp. exposure included Farmer's Lung, Malt-Worker's Lung, Esparto Worker's Lung, and Woodworker's lung (Sawmill-workers). No studies directly addressed serological testing in Tobacco Worker's lung, Compost Lung, or poultry workers. Among Aspergillus species exposure, A. fumigatus was most commonly described; others included A. umbrosus (now A. glaucus), A. clavatus, and A. niger. Antibody tests included ELISA, BALISA, precipitin tests and ImmunoCAP, with a higher sensitivity of ELISA and ImmunoCAP tests compared to precipitin tests. Patients with HP linked to Aspergillus exposures, were positive in 156/290 (53.8%) compared to 96/615 (15.6%) in those with similar occupational exposures without HP. In malt workers with HP 35/53 (66%) had detectable A. clavatus IgG antibody compared to 0/53 A. fumigatus IgG, and 13/74 (18%) exposed but unaffected workers, but are not commercially available.ConclusionsImproved means of establishing or ruling out Aspergillus exposure are required, given the negative consequences for patients of continued Aspergillus inhalation. Modern studies with commercially available Aspergillus IgG antibody assays are required to define appropriate cutoffs for HP, given numerous studies published for chronic pulmonary aspergillosis.

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.

Diagnostic Approach to Hypersensitivity Pneumonitis: A Report of Two Cases

Hypersensitivity pneumonitis (HP) is a bronchopulmonary granulomatosis of immunological mechanism, caused by an aberrant response to an inhaled exposure, which results in mostly T cell-mediated inflammation, granuloma formation, and fibrosis in some cases. The most common forms are bird breeder's disease and farmer's lung disease. The diagnosis of HP is based on the presence of compatible symptoms, the notion of exposure to antigens known to be pathogenic, and the existence of interstitial and bronchiolar images on the thoracic scan, lymphocytosis in the alveolar lavage, and precipitins. Chronic forms, in case of insidious exposure, especially in poultry, may evolve into pulmonary fibrosis with a poor prognosis. Through this work, we want to underline the frequency of this disease in our country, its heterogeneity as well as the difficult early diagnosis. Finally, we will investigate the therapeutic effect of corticosteroids in the early stages and the antifibrotic treatment in fibrotic forms.

Evaluation of cases with hypersensitivity pneumonia: 10 year analysis

INTRODUCTION

The aim of this study was to examine the clinical features of hypersensitivity pneumonia (HP) cases, diagnostic methods, and related conditions in our hospital, which is a reference clinic in Turkey for chest disease.

METHODS

The population of this retrospective cross-sectional study consists of all hypersensitivity pneumonia patients followed in a tertiary hospital between 2010 and 2019. The data of 78 patients were included in the analysis. Data were grouped by source of exposure (occupational, environmental, and cryptogenic) by examining the files of the patients.

RESULTS

Occupational risk factors were detected in 29 (37.2%) of the cases, environmental risk factors were found in 24 (30.8%) cases, neither occupational nor environmental risk factors were detected in 25 (32%) cases, and they were evaluated as cryptogenic. The time from the onset of symptoms to diagnosis was 15.8 ± 26.6 months. The time from the onset of symptoms to diagnosis was found to be longer in the group with occupational risk factors compared with the other groups and was statistically significant (0.044).

CONCLUSION

HP is a immune-mediated interstitial lung disease induced by repeated exposure to environmental and occupational antigens. Etiological agent can be detected in HP patients by detailed questioning of occupational and environmental exposure that may be associated with the onset of symptoms in cases with suspected HP.