Utility of a provocation test for diagnosis of chronic pigeon Breeder's disease

[Diagnosis and Treatment of Hypersensitivity Pneumonitis - S2k Guideline of the German Respiratory Society and the German Society for Allergology and Clinical Immunology]

Hypersensitivity pneumonitis (HP) is an immune-mediated interstitial lung disease (ILD) in sensitized individuals caused by a large variety of inhaled antigens. The clinical form of acute HP is often misdiagnosed, while the chronic form, especially the chronic fibrotic HP, is difficult to differentiate from other fibrotic ILDs. The present guideline for the diagnosis and treatment of HP replaces the former German recommendations for the diagnosis of HP from 2007 and is amended explicitly by the issue of the chronic fibrotic form, as well as by treatment recommendations for the first time. The evidence was discussed by a multidisciplinary committee of experts. Then, recommendations were formulated for twelve questions on important issues of diagnosis and treatment strategies. Recently published national and international guidelines for ILDs and HP were considered. Detailed background information on HP is useful for a deeper insight into HP and the handling of the guideline.

Japanese clinical practice guide 2022 for hypersensitivity pneumonitis

Considering recently published two guidelines for the diagnosis of hypersensitivity pneumonitis (HP), the Japanese Respiratory Society (JRS) has now published its own Japanese clinical practice guide for HP. Major types of HP in Japan include summer-type, home-related, bird-related, farmer's lung, painter's lung, humidifier lung, and mushroom grower's lung. Identifying causative antigens is critical for increasing diagnostic confidence, as well as improving prognosis through appropriate antigen avoidance. This guide proposes a comprehensive antigen questionnaire including the outbreak sources reported in Japan. Drawing on the 2021 CHEST guideline, this guide highlights the antigen identification confidence level and adaptations for environmental surveys. The detection of specific antibodies against causative antigens is an important diagnostic predictor of HP. In Japan, the assessments of bird-specific IgG (pigeons, budgerigars) and the Trichosporon asahii antibody are covered by medical insurance. Although this guide adopts the 2020 ATS/JRS/ALAT guideline diagnostic criteria based on the combination of imaging findings, exposure assessment, bronchoalveolar lavage lymphocytosis, and histopathological findings, it added some annotations to facilitate the interpretation of the content and correlate the medical situation in Japan. It recommends checking biomarkers; seasonal changes in the KL-6 concentration (increase in winter for bird-related HP/humidifier lung and in summer for summer-type HP) and high KL-6 concentrations providing a basis for the suspicion of HP. Antigen avoidance is critical for disease management of HP. This guide also addresses the pharmacological management of HP, highlighting the treatment strategy for fibrotic HP including combination therapies with anti-inflammatory/immunosuppressive and antifibrotic drugs.

Diagnosis and Pharmacologic Management of Fibrotic Interstitial Lung Disease

Interstitial lung disease is an umbrella term that encompasses a spectrum of parenchymal lung pathologies affecting the gas exchanging part of the lung. While many of these disease entities are not fibrotic in nature, a number can lead to pulmonary fibrosis which may or may not progress over time. Idiopathic pulmonary fibrosis is the prototypical, progressive fibrotic interstitial lung disease, which can lead to worsening hypoxemic respiratory failure and mortality within a number of years from the time of diagnosis. The importance of an accurate and timely diagnosis of interstitial lung diseases, which is needed to inform prognosis and guide clinical management, cannot be overemphasized. Developing a consensus diagnosis requires the incorporation of a variety of factors by a multidisciplinary team, which then may or may not determine a need for tissue sampling. Clinical management can be challenging given the heterogeneity of disease behavior and the paucity of controlled trials to guide decision making. This review addresses current paradigms and recent updates in the diagnosis and pharmacologic management of these fibrotic interstitial lung diseases.

Validation of inhalation challenge test and serum immunoglobulin G test for bird-related fibrotic hypersensitivity pneumonitis

BACKGROUND

The inhalation challenge test is considered to be the item for diagnosis of hypersensitivity pneumonitis (HP) and identifying the causative antigen in patients with fibrotic HP. However, the inhalation challenge test is not widely used.

OBJECTIVE

To evaluate the values of the inhalation challenge test by comparing with serum immunoglobulin (Ig)G test.

METHODS

This was a single-center, retrospective study. The patients with fibrotic HP were diagnosed pathologically by surgical lung biopsy or transbronchial lung cryobiopsy and were assumed to have bird-related fibrotic HP if they had a history of obvious avian exposure.

RESULTS

On the basis of pathologic findings and history of avian exposure, 43 of 86 patients were diagnosed with having bird-related fibrotic HP. In 43 patients with bird-related fibrotic HP, 15 (35%) were positive for anti-bird IgG antibody and 36 (84%) were positive for the inhalation challenge test; in addition, the specificity of the inhalation challenge test was 67%. Patients with both positive results from inhalation challenge test and anti-bird IgG antibodies had a 2.7% decline in annual forced vital capacity (FVC) before the inhalation (P = .02). In patients with positive result from inhalation challenge test and negative result from anti-bird IgG antibodies, the annual FVC decreased by 5.8% (P = .03). FVC was not consistent in patients with positive result from the anti-bird IgG antibodies.

CONCLUSION

The inhalation challenge test for bird-related fibrotic HP was more sensitive than the anti-bird IgG antibodies. Furthermore, the inhalation challenge test could select patients with similar disease progression.

Alternative Gene Expression by TOLLIP Variant Is Associated With Lung Function in Chronic Hypersensitivity Pneumonitis

BACKGROUND

Chronic hypersensitivity pneumonitis (CHP) is a heterogeneous fibrotic interstitial pneumonia resulting from the immune response of susceptible individuals to inhaled antigens. Genetic predispositions have been suggested in CHP; however, the link between susceptibility genes and fibrotic progression has not been elucidated fully. Recent data suggest that variants in Toll-interacting protein (TOLLIP) are associated with lung diseases.

RESEARCH QUESTION

Can TOLLIP variants be associated with any clinical features in patients with CHP?

STUDY DESIGN AND METHODS

We genotyped rs5743899 and rs3750920 in TOLLIP and analyzed the association with clinical parameters in 101 patients with CHP (67 for the retrospective cohort and 34 for the prospective cohort). We evaluated the expression of TOLLIP and fibrogenic signals in affected lung tissues and periostin in sera. Furthermore, we performed immunologic analysis in the lungs and sera.

RESULTS

The rs5743899 GG genotype was associated with rapid deterioration in FVC over time, which demonstrated significant annual decline in the retrospective cohort (vs AA, P = .0006; vs AG, P < .0001), prospective cohort (vs AA, P < .0001; vs AG, P = .003), and combined cohort (both P < .0001). The patients with the GG genotype demonstrated lower transcription-translation levels of TOLLIP as well as increased phosphorylation of Smad2 and inhibitor of kappa B in the lung tissues and exhibited higher serum levels of periostin, IL-1α, IL-1β, IL-6, IL-8, tumor necrosis factor α, and IFN-γ.

INTERPRETATION

The functional changes by TOLLIP variant were associated with rapid FVC decline through dysregulated Smad/transforming growth factor β and NF-κB signaling in CHP.

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.

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

BACKGROUND

The purpose of this summary is to provide a synopsis of 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, and 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.

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. 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.

Exposure Assessment Tools for Hypersensitivity Pneumonitis. An Official American Thoracic Society Workshop Report

This report is based on proceedings from the Exposure Assessment Tools for Hypersensitivity Pneumonitis (HP) Workshop, sponsored by the American Thoracic Society, that took place on May 18, 2019, in Dallas, Texas. The workshop was initiated by members from the Environmental, Occupational, and Population Health and Clinical Problems Assemblies of the American Thoracic Society. Participants included international experts from pulmonary medicine, occupational medicine, radiology, pathology, and exposure science. The meeting objectives were to 1) define currently available tools for exposure assessment in evaluation of HP, 2) describe the evidence base supporting the role for these exposure assessment tools in HP evaluation, 3) identify limitations and barriers to each tool's implementation in clinical practice, 4) determine which exposure assessment tools demonstrate the best performance characteristics and applicability, and 5) identify research needs for improving exposure assessment tools for HP. Specific discussion topics included history-taking and exposure questionnaires, antigen avoidance, environmental assessment, specific inhalational challenge, serum-specific IgG testing, skin testing, lymphocyte proliferation testing, and a multidisciplinary team approach. Priorities for research in this area were identified.

Assessment and Management of Occupational Hypersensitivity Pneumonitis

The diagnosis and treatment of occupational hypersensitivity pneumonitis (OHP) remain complex and challenging in the absence of diagnostic gold standards or clinical guidelines. This review provides an update of the recent literature regarding the different presentations of OHP and the diagnostic yield and value of the diagnostic tests currently available, which include occupational and medical history, laboratory tests (serum-specific immunoglobulins, environmental sampling), imaging, bronchoalveolar lavage, transbronchial biopsy, transbronchial cryobiopsy, surgical lung biopsy, and specific inhalation challenges. These tools provide a precise differential diagnosis within the framework of interstitial lung diseases. However, among the chronic fibrotic forms, distinguishing OHP from sarcoidosis, nonspecific interstitial pneumonia and idiopathic pulmonary fibrosis remains a diagnostic challenge. Avoidance of exposure is pivotal for OHP management, whereas corticosteroids are fundamental in the pharmacological approach to this disease. In addition, studies describing the long-term benefits of immunosuppressive and antifibrotic agents have increased the use of these treatments in OHP.

Inhalation challenge test using pigeon eggs for chronic hypersensitivity pneumonitis

BACKGROUND

Chronic hypersensitivity pneumonitis (CHP) remains a diagnostic challenge. The process of collecting and extracting serum and droppings from causative animals for the inhalation challenge test is complicated and the risk of inducing disease progression exists.

OBJECTIVE

To investigate the utility and safety of an inhalation challenge test using pigeon eggs.

METHODS

Pigeon eggs were pasteurized and mixed with a saline solution to produce an inhalation fluid. An inhalation challenge test was conducted on 19 patients with bird-related CHP and 17 patients with interstitial lung disease other than bird-related CHP. To identify antigens in pigeon eggs, the antigen-antibody responses of the pigeon eggs and serum from patients were evaluated using Western blotting.

RESULTS

The mean changes in C-reactive protein, alveolar-arterial oxygen difference, erythrocyte sedimentation rate, and lactate dehydrogenase significantly increased by 0.32 mg/dL (P = .014), 7.8 Torr (P = .002), 1.4 mm/h (P = .012), and 5.4 U/mL (P = .0019), respectively, in bird-related CHP group compared to the control 24 hours after the inhalation challenge test. Furthermore, within 24 hours of the inhalation test, the mean forced vital capacity decreased by 2.3% in the bird-related CHP group compared with a decline of 0.05% in the control group (P = .035). Serum collected from seven bird-related CHP patients who underwent the inhalation challenge test and reacted to antigens with molecular weights of 37-75 KDa, and these molecular weights were consistent with egg albumin and globulin.

CONCLUSION

Since a mild response was observed after the inhalation challenge test using pigeon eggs, this test was an obvious candidate for diagnosing bird-related CHP.

Hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is a complex syndrome caused by the inhalation of a variety of antigens in susceptible and sensitized individuals. These antigens are found in the environment, mostly derived from bird proteins and fungi. The prevalence and incidence of HP vary widely depending on the intensity of exposure, the geographical area and the local climate. Immunopathologically, HP is characterized by an exaggerated humoral and cellular immune response affecting the small airways and lung parenchyma. A complex interplay of genetic, host and environmental factors underlies the development and progression of HP. HP can be classified into acute, chronic non-fibrotic and chronic fibrotic forms. Acute HP results from intermittent, high-level exposure to the inducing antigen, usually within a few hours of exposure, whereas chronic HP mostly originates from long-term, low-level exposure (usually to birds or moulds in the home), is not easy to define in terms of time, and may occur within weeks, months or even years of exposure. Some patients with fibrotic HP may evolve to a progressive phenotype, even with complete exposure avoidance. Diagnosis is based on an accurate exposure history, clinical presentation, characteristic high-resolution CT findings, specific IgG antibodies to the offending antigen, bronchoalveolar lavage and pathological features. Complete antigen avoidance is the mainstay of treatment. The pharmacotherapy of chronic HP consists of immunosuppressive drugs such as corticosteroids, with antifibrotic therapy being a potential therapy for patients with progressive disease.

Diagnostic accuracy and safety of inhalation challenge tests for bird fancier's lung-Systematic review and meta-analysis

OBJECTIVE

To assess the diagnostic accuracy of inhalation challenge tests for bird fancier's lung and related adverse reactions.

DESIGN

We performed a systematic review and meta-analysis for the diagnostic test accuracy of inhalation challenge tests and a systematic review for adverse events of the tests. We evaluated the risk of bias and applicability of the included articles for diagnostic test accuracy with the modified Quality Assessment of Diagnostic Accuracy Studies-2 tool. We used hierarchical summary receiver operating characteristic (HSROC) curve analysis to evaluate the sensitivity and specificity of challenge tests and assessed subjective adverse reactions and steroid treatment use. Sensitivity was calculated by fixing specificity at 99% from the HSROC curve.

DATA SOURCES

We searched for articles evaluating the diagnostic accuracy of inhalation challenge tests or describing adverse reactions in Medline, Embase, the Cochrane Library, the International Clinical Trials Registry Platform, and Web of Science.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

We included randomized control trials, prospective or retrospective cohort studies, or case-control studies assessing the diagnostic test accuracy of inhalation challenge tests for bird fancier's lung. For adverse effects review, we included the same articles, and case series or case reports reporting adverse reactions of inhalation challenge tests.

RESULTS

In our review of 12 articles, the diagnostic accuracy of inhalation challenge tests was substantially high. Point estimate of sensitivity when calculated with a fixed specificity of 99% was 99%. Among 873 patients, 6 needed steroid treatment for adverse reactions; however, no death occurred due to acute exacerbation following a challenge test.

CONCLUSIONS

Inhalation challenges for bird fancier's lung could be accurate and safe diagnostic procedures and may be considered both as rule-in and rule-out tests in tertiary care centres. However, caution is required regarding overestimation of diagnostic yield due to risk of bias. Systematic review registration: University hospital Medical Information Network Clinical Trials Registry (UMIN000038799).

Fibrotic Hypersensitivity Pneumonitis: Diagnosis and Management

Fibrotic hypersensitivity pneumonitis is a complex interstitial lung disease that is not entirely understood. In its chronic and fibrotic form, hypersensitivity pneumonitis is one of the main mimickers of idiopathic pulmonary fibrosis (IPF). Distinguishing between these two conditions is challenging but is of particular clinical relevance. Two approved therapies are available for IPF, and a considerable number of clinical trials are now exploring newer pharmacological options. This impressive research effort is a consequence of new pathogenetic understanding, updated diagnostic criteria and a long history of pharmacological trials. Conversely, current knowledge gaps on pathogenesis of chronic hypersensitivity pneumonitis, coupled with lack of validated diagnostic criteria, make the management of this disease an unsolved clinical challenge. This also reflects the paucity of therapeutic clinical trials in this field. In this review, we describe the current evidence and the possible future options to approach this complex disease.

Hypersensitivity Pneumonitis and (Idiopathic) Pulmonary Fibrosis Due to Feather Duvets and Pillows

INTRODUCTION

Exposure to feather bedding may be an unnoticed cause of hypersensitivity pneumonitis (HP) and idiopathic pulmonary fibrosis (IPF). Thus, an in-depth clinical study of the diagnosis of patients with suspected HP and IPF is required in order to determine their etiologies. The objective of the present study is to raise awareness of HP and pulmonary fibrosis due to exposure to feather bedding, and to study the prevalence and describe long-term outcomes.

METHODS

We describe a series of 33 patients diagnosed with HP and pulmonary fibrosis due to feather bedding exposure and followed over a 10-year period. The patients were from a subgroup of 127 individuals with HP undergoing in-depth evaluation using a diagnostic protocol at a regional referral center.

RESULTS

Eleven (33%) patients were clinically diagnosed with acute HP and 22 (67%) with chronic HP. Ten (45%) chronic HP patients showed a high resolution computed tomography (HRCT) pattern of usual interstitial pneumonia (UIP) with suspected IPF. The prevalence of HP was 6.2/100 000 feather bedding users (compared with 54.6 per 100 000 bird-breeders). The survival rates of patients over the 10-year period was 100% for acute HP and 64% for chronic HP.

CONCLUSIONS

In a series of HP patients, the diagnosis was attributed to feather bedding exposure in 26%. UIP pattern on HRCT was present in nearly half of the chronic cases. The survival of patients with chronic HP at ten years was 64%, despite avoiding further exposure.

Acute inflammatory and immunologic responses against antigen in chronic bird-related hypersensitivity pneumonitis

BACKGROUND

Hypersensitivity pneumonitis (HP) is an immune-mediated lung disease induced by the inhalation of a wide variety of antigens and a persistent antigen exposure induces inevitably pulmonary fibrosis in chronic HP. Although neutrophils, Th1 and Th17 cells contribute to lung inflammation in acute phase of HP, there is no clear explanation as to how the immunological reaction occurs just after the inhalation of causative antigens in the chronic phase of HP.

METHODS

We examined the inflammatory and immunologic profiles before and after the inhalation provocation test (IPT) in serum and bronchoalveolar lavage fluid (BALF) from patients with chronic bird-related HP (BRHP) and other interstitial lung diseases (ILDs). We analyzed BALF samples from 39 patients (19 BRHP and 20 other ILDs) and serum samples from 25 consecutive patients (20 BRHP and 5 other ILDs) who underwent the IPT.

RESULTS

A significant increase of neutrophils was observed in the BALF from the BRHP patients following the IPT. Neutrophil chemoattractants, namely, granulocyte colony-stimulating factor, IL-6, IL-8, IL-17, and CXCL2 significantly increased in both the serum and BALF of the BRHP patients after the IPT. Serum IFN-γ and CXCL10, cytokines/chemokines that contributed to Th1 inflammation, were also significantly increased in BRHP following the IPT.

CONCLUSIONS

This study demonstrated the exposure to the causative antigen provoked acute neutrophilic and Th1 immunologic responses similar to acute HP even in the chronic phase of HP.

[Hypersensitivity pneumonitis in children]

Hypersensitivity pneumonitis (HP) is an interstitial lung disease caused by an immune response to a variety of antigens to which patients have been previously sensitised. It can occur at any age. In children, it is a rare disease, probably under-diagnosed, with an estimated prevalence of 4 per million. The paediatric forms are not really different from those of adults but present some particularities. Avian exposure is by far the most frequent cause of HP, accounting for nearly two-thirds of cases. Although there is no current recommendation for the diagnosis of HP, it is commonly considered that the diagnosis can be made with confidence on the combination of (1) compatible respiratory symptoms, (2) exposure to a known offending antigen, (3) lymphocytic alveolitis, (4) decreased transfer factor for carbon monoxide or hypoxia on exertion and (5) compatible radiologic features. The treatment is based on antigen avoidance that must be complete and definitive. Corticosteroids can be necessary in severe forms. The prognosis of HP in children is better than in adults, with a full clinical and functional recovery in the majority of cases after complete antigenic withdrawal.

Hypersensitivity pneumonitis: A new strategy for serodiagnosis and environmental surveys

We propose a strategy for serodiagnosis of hypersensitivity pneumonitis (HP): 1) question patients about their private or occupational activity, or visit him on site; 2) select panels of six somatic specific antigens appropriate for each type of exposure; 3) and use ELISA to test concomitantly two recombinant antigens highly specific to Farmer's lung, Metalworking-fluid HP, and for Bird fancier's lung. The serodiagnosis provides an immunological argument that may complete radiological, functional lung exploration and clinical features; 4) If the serodiagnosis is negative but the suspicion of HP is strong, a microbial analysis of the patient's specific exposure is conducted; 5) "A la carte" antigens are produced from the microorganisms isolated in the patient's environment sample and tested; 6) Finally, the patient may be asked to undergo a specific inhalation challenge with the offending antigens in a safety cabin, or to avoid his usual environment for a few days.

Current and emerging techniques for the diagnosis of hypersensitivity pneumonitis

INTRODUCTION

Hypersensitivity pneumonitis (HP) is the result of an immunologically induced inflammation of the lung parenchyma in response to inhalation exposure to a large variety of antigens in genetically susceptible individuals. HP shares clinical and radiological features with other acute and chronic interstitial lung diseases and is sometimes difficult to diagnose if exposure to an antigenic agent is not detected. Several classifications and diagnostic criteria have been proposed but are not currently recommended by guidelines from any scientific society. However, advances have been made over the past ten years in improving the diagnosis of HP. Areas covered: This article will provide a summary of the different classification and diagnostic criteria proposed in acute and chronic forms of HP. In addition, we review current diagnostic procedures including antigen detection, high resolution computed tomography, histopathology and provide an overview of emerging techniques. Expert commentary: Important changes are occurring in the field of HP and knowledge of the disease will likely progress enormously in the coming 5 to 10 years as many techniques continue to be developed, including genomic signature and diagnostic biomarkers.

Small airway dysfunction in chronic hypersensitivity pneumonitis

BACKGROUND AND OBJECTIVE

Lung biopsies from patients with hypersensitivity pneumonitis (HP) have demonstrated small airway (SA) involvement, but there is no information concerning SA function in HP, and it is unknown whether pharmacological treatment could modify its function. SA function in patients with chronic HP using ultrasonic pneumography (UPG) and impulse oscillometry (IOS) was explored. We also compared initial results with those obtained after 4 weeks of standardized treatment with azathioprine and prednisone.

METHODS

The study group consisted of adults with recent diagnoses of HP. All patients completed UPG, IOS, spirometry, body plethysmography, single-breath carbon monoxide diffusing capacity (DL_CO ) and the 6-min walk test (6MWT). The fraction of exhaled nitric oxide (FE_NO ) was obtained to assess eosinophilic airway inflammation. Measurements were taken at diagnosis and after 4 weeks of treatment.

RESULTS

A total of 20 consecutive patients (16 women) with chronic HP participated in the study. Median age was 50 years (interquartile range (IQR): 42-54). At diagnosis, the UPG phase 3 slope was abnormally high, consistent with maldistribution of ventilation. For IOS, all patients had low reactance at 5 Hz (X5) and elevated reactance area (AX) reflecting low compliance, and only eight (40%) patients had elevated R5 (resistance at 5 Hz (total)) and R5-20 (resistance at 5 Hz-resistance at 20 Hz (peripheral)) attributed to SA resistance. In contrast, FE_NO parameters were within normal limits. After treatment, forced vital capacity (FVC), the 6-min walk distance and the distribution of ventilation showed significant improvement, although DL_CO did not.

CONCLUSION

Patients with chronic HP have SA abnormalities that are partially revealed by the UPG and IOS tests. Lung volumes, but not gas exchange, improved after treatment with azathioprine and prednisone.

Fibrotic Hypersensitivity Pneumonitis: Key Issues in Diagnosis and Management

The diagnosis of hypersensitivity pneumonitis (HP) relies on the clinical evaluation of a number of features, including a history of significant exposure to potentially causative antigens, physical examination, chest CT scan appearances, bronchoalveolar lavage lymphocytosis, and, in selected cases, histology. The presence of fibrosis is associated with higher morbidity and mortality. Differentiating fibrotic HP from the idiopathic interstitial pneumonias can be a challenge. Furthermore, even in the context of a clear diagnosis of fibrotic HP, the disease behaviour can parallel that of idiopathic pulmonary fibrosis in a subgroup, with inexorable progression despite treatment. We review the current knowledge on the diagnosis, management, and prognosis of HP with particular focus on the fibrotic phenotype.

Protein antigen of bird-related hypersensitivity pneumonitis in pigeon serum and dropping

BACKGROUND

Avian antigen is a common cause of hypersensitivity pneumonitis (HP). Inhalation challenge with pigeon serum and pigeon dropping extract (PDE) elicits a hypersensitivity reaction in patients with bird-related hypersensitivity pneumonitis (BRHP), but the antigenic components in these materials have yet to be fully elucidated.

METHOD

Pigeon serum, pigeon intestine homogenates, and PDE were immunoblotted with serum samples from 8 patients with BRHP, 2 patients with summer-type HP, 2 patients with humidifier lung, and 3 healthy volunteers. Among the protein spots found in both pigeon serum and PDE, those that reacted with sera from BRHP patients were identified by mass spectrometry. Immunoassays using recombinant protein were performed to confirm the antigenicity of the identified protein. Cytokine production by peripheral blood mononuclear cells (PBMCs) stimulated with recombinant protein was also assessed.

RESULTS

Immunoglobulin lambda-like polypeptide-1 (IGLL-1) was identified from all spots on 2-DE immunoblots of both pigeon serum and PDE. The BRHP patients exhibited higher levels of serum IgG antibody against the recombinant IGLL-1 (rIGLL-1) compared to the control subjects, as well as a stronger PBMCs proliferative response to rIGLL-1. Cytokine production by PBMCs from BRHP patients after rIGLL-1 exposure indicated that the protein could induce Th1 prone immune responses: an increase in TNF-α and an absence of elevated IL-10 production.

CONCLUSIONS

Pigeon IGLL-1 was identified as the BRHP antigen present in both pigeon serum and PDE.

Factors associated with positive inhalation provocation test results in subjects suspected of having chronic bird-related hypersensitivity pneumonitis

BACKGROUND

Chronic bird-related hypersensitivity pneumonitis (BRHP) is often misdiagnosed as other interstitial lung diseases. While the utility of the inhalation provocation test (IPT) has been reported, the test is not commonly performed. In this study, we aimed to identify significant clinical variables associated with positive inhalation provocation test results in subjects suspected of having chronic BRHP. This would help clinicians decide whether to perform IPT in patients suspected of having chronic BRHP in real-life practice.

METHODS

We retrospectively evaluated 107 patients who underwent the IPT for suspected chronic BRHP. We used the IPT as the gold standard diagnostic tool for chronic BRHP.

RESULTS

Specific antibodies against pigeon dropping extract were documented in 52% of the IPT-positive patients but also in 38% of the IPT-negative patients (p=0.172). By using the logistic regression model, three significant predictors of IPT results were identified as follows: (1) a history of raising birds (odds ratio [OR] 3.112), (2) exposure to birds from the surrounding environment (OR 7.321), (3) white blood cell count (×10²/μl; OR 0.959).

CONCLUSIONS

This study demonstrates that current or past exposure to avian antigens is a positive predictor of positive IPT results in patients suspected of having chronic BRHP.

Occupational hypersensitivity pneumonitis: an EAACI position paper

The aim of this document was to provide a critical review of the current knowledge on hypersensitivity pneumonitis caused by the occupational environment and to propose practical guidance for the diagnosis and management of this condition. Occupational hypersensitivity pneumonitis (OHP) is an immunologic lung disease resulting from lymphocytic and frequently granulomatous inflammation of the peripheral airways, alveoli, and surrounding interstitial tissue which develops as the result of a non-IgE-mediated allergic reaction to a variety of organic materials or low molecular weight agents that are present in the workplace. The offending agents can be classified into six broad categories that include bacteria, fungi, animal proteins, plant proteins, low molecular weight chemicals, and metals. The diagnosis of OHP requires a multidisciplinary approach and relies on a combination of diagnostic tests to ascertain the work relatedness of the disease. Both the clinical and the occupational history are keys to the diagnosis and often will lead to the initial suspicion. Diagnostic criteria adapted to OHP are proposed. The cornerstone of treatment is early removal from exposure to the eliciting antigen, although the disease may show an adverse outcome even after avoidance of exposure to the causal agent.

A diagnostic model for chronic hypersensitivity pneumonitis

The objective of this study was to develop a diagnostic model that allows for a highly specific diagnosis of chronic hypersensitivity pneumonitis using clinical and radiological variables alone. Chronic hypersensitivity pneumonitis and other interstitial lung disease cases were retrospectively identified from a longitudinal database. High-resolution CT scans were blindly scored for radiographic features (eg, ground-glass opacity, mosaic perfusion) as well as the radiologist's diagnostic impression. Candidate models were developed then evaluated using clinical and radiographic variables and assessed by the cross-validated C-statistic. Forty-four chronic hypersensitivity pneumonitis and eighty other interstitial lung disease cases were identified. Two models were selected based on their statistical performance, clinical applicability and face validity. Key model variables included age, down feather and/or bird exposure, radiographic presence of ground-glass opacity and mosaic perfusion and moderate or high confidence in the radiographic impression of chronic hypersensitivity pneumonitis. Models were internally validated with good performance, and cut-off values were established that resulted in high specificity for a diagnosis of chronic hypersensitivity pneumonitis.

Hypersensitivity pneumonitis : a broader perspective

Hypersensitivity pneumonitis (HP) represents a group of lung disorders caused by the inhalation of a wide variety of organic particles by susceptible individuals. HP occurs mainly in nonsmokers, but smoking may promote an insidious and chronic disease. The prevalence of HP is difficult to estimate accurately since several antigens can produce the disease, but the range spans infancy to old age. Regardless of the causative antigen or its environmental setting, the clinical manifestations are essentially the same. Three different clinical presentations have been recognized: acute, subacute, and chronic. In the acute form, patients show flu-like symptomatology, followed by dyspnea and dry cough. Symptoms subside a few hours or days later. The subacute and chronic forms result from recurrent low-level antigen exposure and are characterized by progressive dyspnea and dry cough. Other constitutional symptoms such as fatigue, anorexia, and weight loss can be apparent. Fever may occur in the subacute form. Importantly, chronic HP may evolve insidiously or may result from repeated acute/subacute episodes. Recurrent acute, subacute, and chronic HP may progress to irreversible lung fibrosis or provoke emphysematous changes.HP can be difficult to identify, and precise diagnosis requires a history of exposure and a constellation of clinical, imaging, laboratory, bronchoalveolar lavage and pathologic findings. General laboratory tests show an increase of acute phase reactants. Specific precipitating antibodies, when present, are evidence of antigen exposure, and are a hallmark for diagnosis. Chest radiograph usually reveals widespread ground-glass attenuation, and nodular or reticulonodular shadowing. High-resolution CT features include diffuse or patchy ground-glass opacities with small poorly defined nodules and air trapping. Pulmonary function tests are characterized by a predominantly restrictive ventilatory defect with loss of lung volume and hypoxemia at rest that worsens with exercise. Bronchoalveolar lavage reveals a significant increase in lymphocytes, mostly over 40%. In the acute form there is also an increase in neutrophils. Antigen-induced lymphocyte proliferation, and environmental or laboratory-controlled inhalation challenge, may be used for diagnostic purposes and can help to establish a diagnosis of insidious forms of HP. In subacute or chronic cases, lung biopsy may be necessary. Typical findings include bronchiolitis, lymphocytic alveolitis, and loosely formed granulomas, although occasionally other morphologic patterns such as nonspecific interstitial pneumonia may exist. Treatment focuses on avoiding further exposure to the offending antigen(s). Corticosteroids are recommended in subacute and chronic forms. The usual regimen consists of initial high doses of systemic corticosteroid (e.g. prednisone 0.5-1.0 mg/kg/day), followed by gradual tapering.

Changes in PH in exhaled breath condensate after specific bronchial challenge test in patients with chronic hypersensitivity pneumonitis: a prospective study

Background

The aim of this study was to investigate the influence of the specific inhalation challenge (SIC) on changes of pH values in exhaled breath condensate (EBC) in patients with hypersensitivity pneumonitis (HP).

Methods

A prospective study of 85 patients with suspected HP, of whom 63 were diagnosed with HP due to exposure to avian or fungal antigens. In all cases, EBC samples were collected before and after completion of the SIC and pH values were determined.

Results

Taken as a whole, patients with HP did not present changes in EBC pH after SIC. However, considering only patients with exposure to molds, those diagnosed with HP had a significantly more acid pH post-SIC than those with another diagnosis (p = 0.011). This fact is not observed in patients exposed to bird’s antigens. A ROC curve showed that a reduction in EBC pH of 0.3 units or more after SIC in patients diagnosed with HP due to exposure to molds had a sensitivity of 30 % (CI: 12.8 to 54.3 %) and a specificity of 100 % (CI: 65.5 to 100 %).

Conclusion

EBC pH may be useful in interpreting SIC results in patients with HP, especially in those patients exposed to molds. Further studies are now required to test the validity of these proposals.

Antigen avoidance tests for diagnosis of chronic hypersensitivity pneumonitis

BACKGROUND

Chronic hypersensitivity pneumonitis (HP) is induced by the inhalation of specific antigens. Patients with chronic HP may be able to improve their prognosis by avoiding these antigens. Chronic HP is often difficult to distinguish from idiopathic interstitial pneumonias (IIPs).

OBJECTIVE

This study was performed to find out how antigen avoidance tests contribute to the diagnosis of chronic HP.

METHODS

A retrospective analysis was conducted on 265 patients who underwent 2-week antigen avoidance tests between April 2002 and March 2012. The patients were classified into the following categories: acute HP, chronic HP, collagen vascular disease-associated interstitial pneumonia (CVD-IP), lung dominant connective tissue disease (LD-CTD), and IIPs. The following seven clinical parameters were evaluated: vital capacity, alveolar-arterial oxygen pressure difference, Krebs von den Lungen-6, surfactant protein-D, white blood cell count, C-reactive protein, and body temperature. These parameters were compared between the chronic HP group and a control group consisting of CVD-IP, LD-CTD, and IIPs.

RESULTS

One-hundred and ninety-six patients with chronic HP and 43 control subjects were evaluated. All clinical parameters improved significantly in the chronic HP group but showed no significant changes in the control group. Four of the parameters changed significantly compared with the control group. Diagnostic criteria established using these data had a sensitivity of 51.0% and a specificity of 80.7%.

CONCLUSIONS

It was difficult to diagnose chronic HP based solely on 2-week antigen avoidance tests; however, improved clinical parameters among patients supported the diagnosis of HP.

Diagnostic yield of specific inhalation challenge in hypersensitivity pneumonitis

Reliable methods are needed to diagnose hypersensitivity pneumonitis. The aim of the study was to establish the diagnostic yield of specific inhalation challenge (SIC) in patients with hypersensitivity pneumonitis. All patients with suspected hypersensitivity pneumonitis in whom SIC was performed (n=113) were included. SIC was considered positive when patients showed a decrease of >15% in forced vital capacity (FVC) or >20% in diffusing capacity of the lung for carbon dioxide, or a decrease of 10% to 15% in FVC accompanied by a temperature increase of 0.5°C within 24 h of inhalation of the antigen. SIC was positive to the agents tested in 68 patients: 64 received a diagnosis of hypersensitivity pneumonitis and SIC results were considered false-positive in the remaining four patients. In the SIC-negative group (n=45), 24 patients received a diagnosis of hypersensitivity pneumonitis and SIC results were considered false-negative, and 21 patients were diagnosed with other respiratory diseases. The sensitivity and specificity of the test were 72.7% and 84%, respectively. Having hypersensitivity pneumonitis caused by an antigen other than birds or fungi predicted a false-negative result (p=0.001). In hypersensitivity pneumonitis, positive SIC testing virtually confirms the diagnosis, whereas negative testing does not rule it out, especially when the antigenic sources are not birds or fungi.

Bronchial inflammation in hypersensitivity pneumonitis after antigen-specific inhalation challenge

BACKGROUND AND OBJECTIVE

The aim of this study is to compare the inflammatory profile before and after specific inhalation challenge (SIC) in induced sputum from patients with hypersensitivity pneumonitis (HP) and to investigate whether different causal antigens define the resulting profile.

METHODS

A prospective study was conducted in 27 patients with HP: 15 patients due to exposure to birds (BHP) and 12 due to exposure to fungi (FHP), confirmed by SIC. Induced sputum was obtained before and/or 24 h after SIC. Cell types were determined by differential cell count using optical microscopy. Interferon-γ, interleukin (IL)-12p70, IL-2, IL-10, IL-8, IL-6, IL-4, IL-5, IL-1β, tumour necrosis factor (TNF)-α and TNF-β levels were measured in the supernatants.

RESULTS

Following SIC, higher sputum neutrophilia levels (P = 0.048) and an increase in IL-8 levels (P = 0.017) were found in patients with FHP than in those with BHP. FHP patients also showed increased IL-1β, IL12-p70 and IL5 levels (P = 0.011, P = 0.036 and P = 0.018, respectively) after SIC. In BHP, a trend towards increases in sputum eosinophils and TH2 cytokines (IL4, IL5) was seen following SIC (P = 0.059, P = 0.068 and P = 0.075 respectively).

CONCLUSIONS

This study shows that bronchial inflammation is present in patients with HP evidenced by increases in sputum neutrophils and eosinophils following exposure to the offending antigen during SIC.

Chronic hypersensitivity pneumonitis in patients diagnosed with idiopathic pulmonary fibrosis: a prospective case-cohort study

BACKGROUND

The clinical features of idiopathic pulmonary fibrosis (IPF) and chronic hypersensitivity pneumonitis can be indistinguishable; the need to eliminate occult environmental factors known to cause pulmonary fibrosis in patients suspected to have IPF during diagnostic evaluation is evident. We aimed to investigate occult, putative causes in the environments of patients diagnosed with IPF using tests beyond those conventionally used.

METHODS

In this case-cohort study, 60 consecutive patients diagnosed with IPF on the basis of the 2000 American Thoracic Society (ATS) and the European Respiratory Society (ERS) criteria were prospectively followed up every 4 months for 6 years between Jan 1, 2004, and Dec 31, 2009. At each visit a uniformly applied questionnaire was administered to these 60 patients to identify occult antigen exposure known to cause hypersensitivity pneumonitis. Patients underwent specific IgG determination, bronchoalveolar lavage, bronchial challenge testing with suspected antigens, and re-review of histopathological features in existing and subsequently obtained surgical lung biopsy samples and from lung explants. Specimens obtained from suspected sources from the patient's environment were subjected to cultures in microbiology laboratory. These clinical data and discussions among pulmonologists and radiologists familiar with IPF were used to confirm the diagnosis in accordance with 2011 ATS, ERS, Japanese Respiratory Society, and Latin American Thoracic Association guidelines; 46 of the 60 patients had IPF according to the 2011 guidelines, and our analyses in this study were focused on these 46 patients.

FINDINGS

20 of the 46 (43%, 95% CI 29-58) patients with IPF according to 2011 guidelines had a subsequent diagnosis of chronic hypersensitivity pneumonitis: nine patients had positive bronchial challenge testing (eight of whom were also IgG positive and six of these patients also had surgical lung biopsy showing a pattern consistent with chronic hypersensitivity pneumonitis); seven were IgG positive plus had histopathology on surgical lung biopsy that was consistent with hypersensitivity pneumonitis; one was IgG positive plus had greater than 20% lymphocytes in bronchoalveolar lavage fluid; and three had findings on surgical lung biopsy that were consistent with subacute hypersensitivity pneumonitis (and IgG positive). Altogether, 29 of 46 patients diagnosed with IPF who had met the 2011 criteria had lung tissue available for histopathology (surgical lung biopsy in 28 patients and explanted lung in two patients, one of whom also had surgical biopsy) during the study period, and 16 of the 20 patients with chronic hypersensitivity pneumonitis had histopathological features on surgical lung biopsy that were consistent with this diagnosis. 26 of the 46 patients remained with a diagnosis of IPF.

INTERPRETATION

Almost half of patients diagnosed with IPF on the basis of 2011 criteria were subsequently diagnosed with chronic hypersensitivity pneumonitis, and most of these cases were attributed to exposure of occult avian antigens from commonly used feather bedding. Our results reflect findings in one centre with recognised expertise in chronic hypersensitivity pneumonitis, and further research and studies at other centres are warranted.

FUNDING

Fondo de Investigaciones Sanitarias; Fundació Privada Cellex; SEPAR 2010.

The use of specific inhalation challenge in hypersensitivity pneumonitis

PURPOSE OF REVIEW

The diagnosis of hypersensitivity pneumonitis remains a dilemma because of the absence of any characteristic features able to distinguish it from other interstitial lung diseases. We analyze the current role of the specific inhalation challenge (SIC) in the diagnosis of this entity.

RECENT FINDINGS

Few descriptions of the use of SIC for the diagnosis of hypersensitivity pneumonitis have been published in recent years. In fact, hypersensitivity pneumonitis is still diagnosed on the basis of clinical criteria, as there is no agreement on the diagnostic utility of SIC. Two major reviews carried out in the past year have concluded that this test is not standardized and is usually unnecessary; however, a third study found that the test can indeed recreate the symptoms and functional abnormalities in the laboratory, and may therefore be of considerable use in the diagnosis of hypersensitivity pneumonitis.

SUMMARY

Hypersensitivity pneumonitis remains a diagnostic challenge. Given that the main cause of the disease is sensitization and hyper-responsiveness to specific antigens in susceptible individuals, SIC is an obvious candidate as the gold standard for diagnosis of this entity. The present review analyzes the reasons for the test's limited use, assesses its diagnostic utility, and proposes a basis for its standardization.

Nationwide epidemiological survey of chronic hypersensitivity pneumonitis in Japan

BACKGROUND

In 1999, a Japanese epidemiological survey of chronic hypersensitivity pneumonitis (HP) showed that summer-type HP was the most prevalent variant of the disease. The number of reported cases of chronic HP has recently been increasing, and the clinical features of the disease seem to have changed. We conducted another nationwide epidemiological survey of chronic HP in Japan to determine better estimates of the frequency and clinical features of the disease.

METHODS

A questionnaire was sent to qualified hospitals throughout Japan, and data on cases of chronic HP diagnosed between 2000 and 2009 were collected.

RESULTS

In total, 222 cases of chronic HP from 22 hospitals were studied. Disease subtypes included bird-related HP (n=134), summer-type HP (n=33), home-related HP (n=25), farmer's lung (n=4), isocyanate-induced HP (n=3), and other types (n=23). The median proportion of lymphocytes in bronchoalveolar lavage fluid was high (24.5%). The primary findings of computed tomography of the chest were ground-glass attenuation and interlobular septal thickening. Centrilobular fibrosis was the major pathological finding on examination of surgical lung biopsy specimens from 93 patients. The median survival time was 83 months.

CONCLUSIONS

The proportion of bird-related HP was higher than that in the previous epidemiological survey, and the proportions of isocyanate-induced HP and farmer's lung were lower. A crucial step in diagnosing chronic HP is to thoroughly explore the possibility of antigen exposure.

Recent advances in hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is a pulmonary disease with symptoms of dyspnea and cough resulting from the inhalation of an allergen to which the subject has been previously sensitized. The diagnosis of HP most often relies on an array of nonspecific clinical symptoms and signs developed in an appropriate setting, with the demonstration of interstitial markings on chest radiographs, serum precipitating antibodies against offending antigens, a lymphocytic alveolitis on BAL, and/or a granulomatous reaction on lung biopsies. The current classification of HP in acute, subacute, and chronic phases is now challenged, and a set of clinical predictors has been proposed. Nonspecific interstitial pneumonitis, usual interstitial pneumonia, and bronchiolitis obliterans organizing pneumonia may be the sole histologic expression of the disease. Presumably, like in idiopathic interstitial pneumonia, acute exacerbations of chronic HP may occur without further exposure to the offending antigen. New offending antigens, such as mycobacteria causing hot tub lung and metalworking fluid HP, have recently been identified and have stimulated further research in HP.

Hypersensitivity pneumonitis

Clinical manifestations of hypersensitivity pneumonitis may closely mimic other interstitial lung diseases, and the disease onset is usually insidious. High-resolution computed tomography and bronchoalveolar lavage are the sensitive and characteristic diagnostic tests for hypersensitivity pneumonitis. The relevant antigen to hypersensitivity pneumonitis cannot be identified in up to 20% to 30% of patients. Clinicians should be aware that hypersensitivity pneumonitis must be considered in all cases of interstitial lung disease, and a detailed environmental exposure history is mandatory.

Hypersensitivity pneumonitis: insights in diagnosis and pathobiology

Hypersensitivity pneumonitis (HP) is a complex syndrome resulting from repeated exposure to a variety of organic particles. HP may present as acute, subacute, or chronic clinical forms but with frequent overlap of these various forms. An intriguing question is why only few of the exposed individuals develop the disease. According to a two-hit model, antigen exposure associated with genetic or environmental promoting factors provokes an immunopathological response. This response is mediated by immune complexes in the acute form and by Th1 and likely Th17 T cells in subacute/chronic cases. Pathologically, HP is characterized by a bronchiolocentric granulomatous lymphocytic alveolitis, which evolves to fibrosis in chronic advanced cases. On high-resolution computed tomography scan, ground-glass and poorly defined nodules, with patchy areas of air trapping, are seen in acute/subacute cases, whereas reticular opacities, volume loss, and traction bronchiectasis superimposed on subacute changes are observed in chronic cases. Importantly, subacute and chronic HP may mimic several interstitial lung diseases, including nonspecific interstitial pneumonia and usual interstitial pneumonia, making diagnosis extremely difficult. Thus, the diagnosis of HP requires a high index of suspicion and should be considered in any patient presenting with clinical evidence of interstitial lung disease. The definitive diagnosis requires exposure to known antigen, and the assemblage of clinical, radiologic, laboratory, and pathologic findings. Early diagnosis and avoidance of further exposure are keys in management of the disease. Corticosteroids are generally used, although their long-term efficacy has not been proved in prospective clinical trials. Lung transplantation should be recommended in cases of progressive end-stage illness.

Pneumomediastinum as a primary manifestation of chronic hypersensitivity pneumonitis

BACKGROUND

Patients with chronic hypersensitivity pneumonitis (HP) can present with an insidious onset of their disease without typical fluctuating flu-like symptoms, and there are only signs of chronic respiratory failure caused by the progressive fibrotic lung disease.

CASE REPORT

A 45-year-old man with a pneumomediastinum and interstitial lung disease was referred for further investigations and therapy. No traumatic event or interventional procedure had occurred prior to referral. The patient had been working in farming for almost 20 years and was exposed in childhood by his father to pigeon breeding from childhood until 20 years ago. He reported dyspnea on exercise for the previous 2 years. High-resolution CT of the lung showed a pneumomediastinum and a fibrotic interstitial lung disease without dominating ground-glass opacities. Specific IgG antibodies were markedly elevated against molds and avian antigens. Bronchoalveolar lavage demonstrated a slightly lymphocytic and neutrophilic alveolitis. After recovering from the pneumomediastinum, an open lung biopsy was performed and a UIP-pattern was detected. An inhalative challenge with hay from the work-place was positive. A diagnosis of chronic farmer's lung was made.

CONCLUSIONS

Pneumomediastinum has been described in other fibrotic lung diseases, but until now it has not been described as a primary manifestation of chronic fibrotic HP. Particularly in cases of concurrent antigen sources, an inhalative challenge could be done, even in a chronic course of HP.

Hypersensitivity pneumonitis: a historical, clinical, and radiologic review

Most cases of hypersensitivity pneumonitis develop only after many years of inhaling allergens, which include microbes, animal or plant proteins, and certain chemicals that form haptens. The initial clinical presentation is either episodes of acute illness with dyspnea and prominent constitutional symptoms, such as fever, or an insidious onset of dyspnea, coughing, and weight loss, sometimes with superimposed acute episodes. The histopathologic process consists of chronic inflammation of the bronchi and peribronchiolar tissue, often with poorly defined granulomas and giant cells in the interstitium or alveoli. Fibrosis and emphysema may develop. The radiologic findings include diffuse ground-glass opacification, centrilobular ground-glass opacities, air trapping, fibrosis, lung cysts, and emphysema. The histologic and radiologic features in some cases may resemble those of usual interstitial pneumonia or nonspecific interstitial pneumonia. The diagnosis usually rests on a variable combination of findings from history, serology, radiography, lung biopsy, and bronchoalveolar lavage, which characteristically reveals a lymphocyte content of more than 30%, often with an increased CD4-to-CD8 ratio of T cells. Treatment includes avoiding the allergen, if possible, and, in severe cases, systemic corticosteroids. The long-term prognosis is usually good, but some patients develop severe respiratory insufficiency, and a few die of the disease.