Needs and Opportunities for Research in Hypersensitivity Pneumonitis

Hypersensitivity pneumonitis: application of a new diagnostic algorithm to a time series of the disease

BACKGROUND

The diagnostic criteria for Hypersensitivity pneumonitis (HP) have changed over time. Our aim is to apply a recent diagnostic algorithm to a historical series of patients diagnosed with HP to assess its distribution according to current diagnostic criteria and the diagnostic confidence achieved.

RESEARCH DESIGN AND METHODS

Application to each patient the algorithm criteria. The diagnosis was HP (≥90%), provisional high (70-89%) or low confidence (51-69%) or non-HP (unlikely) (≤50%); or HP, provisional or non-HP, if they had lung biopsy.

RESULTS

129 patients [mean age 64 ± 12 years; 79 (61.2%) women] were included of which 16 (12.4%) were diagnosed on the basis of high clinical suspicion. After applying the algorithm, 106 patients (82.2%) could be evaluated and 83 (78.3%) had a diagnosis of HP or high confidence. Lung biopsy was able to establish a diagnosis of certainty in another 21 patients and a provisional diagnosis in 9 more [total, 113 (87.6%)]. The 16 patients without strict diagnostic criteria for HP had a low confidence diagnosis. A total of 56 lung biopsies (64.4%) could have been avoided according to the new guidelines.

CONCLUSIONS

The application of this algorithm achieves a high diagnostic yield in HP, significantly reducing the number of lung biopsies required.

Distinct TNF-alpha and HLA polymorphisms associate with fibrotic and non-fibrotic subtypes of hypersensitivity pneumonitis

INTRODUCTION

Since Hypersensitivity Pneumonitis (HP) categorization in fibrotic and nonfibrotic/inflammatory types seems to be more consistent with the distinctive clinical course and outcomes, recent international guidelines recommended the use of this classification. Moreover, fibrotic subtype may share immunogenetic and pathophysiological mechanisms with other fibrotic lung diseases.

AIM

To investigate HLA -A, -B, -DRB1 and TNF-α -308 gene polymorphisms among fibrotic and nonfibrotic HP patients due to avian exposure, also in comparison with asymptomatic exposed controls.

METHODS

We prospectively enrolled 40 HP patients, classified as fibrotic or nonfibrotic/inflammatory, and 70 exposed controls. HLA and TNF-α polymorphisms were determined by polymerase chain reaction-sequence specific primer amplification.

RESULTS

While HLA alleles were not associated to HP susceptibility, fibrotic HP patients showed increased frequencies of HLA A*02 (46.7% vs 25.7%; OR=2.53, p = 0.02) and HLA DRB1*14 (10.0% vs 0.7%; OR=15.44, p=0.02) alleles when compared with exposed controls, although not statistically significant after correction for multiple comparisons. TNF-α G/G genotype (associated with low TNF-α production) frequencies were significantly increased among the non-fibrotic/inflammatory HP patients comparatively to fibrotic presentations (88% vs 60%; RR=0.44; p=0.04) and controls (88% vs 63%, OR 4.33, p=0.037). Also, these patients had a significantly increased frequency of the G allele (94.0% vs 73.3%, RR=0.44, p=0.01), while fibrotic HP patients predominantly presented the A allele (26.7% vs 6.0%, RR=2.28, p=0.01).

CONCLUSIONS

Our results support the hypothesis that fibrotic and non-fibrotic HP subtypes exhibit a distinct profile of TNF-α and HLA polymorphisms, which may be relevant to predict disease course and better define treatment strategies.

When to panic about a panic attack: A challenging case of hypersensitivity pneumonitis

The COVID-19 pandemic has created diagnostic difficulties with the increase in mental health illnesses that often present with nonspecific symptoms, like hypersensitivity pneumonitis. Hypersensitivity pneumonitis is a complex syndrome of varying triggers, onset, severity, and clinical manifestations that can be challenging to diagnose in many cases. Typical symptoms are nonspecific and can be attributed to other entities. There are no pediatric guidelines, which contributes to diagnostic difficulties and delays in treatment. It is particularly important to avoid diagnostic biases, have an index of suspicion for hypersensitivity pneumonitis, and to develop pediatric guidelines as outcomes are excellent when diagnosed and treated promptly. This article discusses hypersensitivity pneumonitis with a focus on the causes, pathogenesis, diagnostic approach, outcomes, and prognosis while using a case to illustrate the diagnostic difficulties worsened by the COVID-19 pandemic.

Hypersensitivity Pneumonitis: Updates in Evaluation, Management, and Ongoing Dilemmas

Hypersensitivity pneumonitis (HP) is a heterogenous disease entity characterized by an aberrant immune response to inhalational antigens. Disease modification hinges on early antigen remediation with a goal to attenuate immune dysregulation. Disease severity and progression are mediated by an interface between degree, type and chronicity of exposure, genetic predisposition, and biochemical properties of the inducing agent. Guidelines have provided a standardized approach; however, decision-making remains with many clinical dilemmas. The delineation of fibrotic and nonfibrotic HP is crucial to identify the differences in clinical trajectories, and further clinical trials are needed to understand optimal therapeutic strategies.

High-Resolution Computed Tomography of Fibrotic Interstitial Lung Disease

While radiography is the first-line imaging technique for evaluation of pulmonary disease, high-resolution computed tomography (HRCT) provides detailed assessment of the lung parenchyma and interstitium, allowing normal anatomy to be differentiated from superimposed abnormal findings. The fibrotic interstitial lung diseases have HRCT features that include reticulation, traction bronchiectasis and bronchiolectasis, honeycombing, architectural distortion, and volume loss. The characterization and distribution of these features result in distinctive CT patterns. The CT pattern and its progression over time can be combined with clinical, serologic, and pathologic data during multidisciplinary discussion to establish a clinical diagnosis. Serial examinations identify progression, treatment response, complications, and can assist in determining prognosis. This article will describe the technique used to perform HRCT, the normal and abnormal appearance of the lung on HRCT, and the CT patterns identified in common fibrotic lung diseases.

Hypersensitivity Pneumonitis: An Updated Diagnostic Guide for Internists

This summary highlights updated definitions, terminology, and classification systems proposed in the diagnosis of hypersensitivity pneumonitis. Clinical presentation, epidemiology, and pathophysiology are reviewed from the most recent data. Radiographic and histopathologic diagnostic criteria are presented in a manner relevant to the practice of general medicine internists, including new guideline recommendations. The role of adjunctive tests, such as serum IgG testing, bronchoalveolar lavage lymphocyte analysis, and pulmonary function testing is discussed in the context of supporting diagnostic confidence for hypersensitivity pneumonitis diagnosis. Finally, new diagnostic algorithms are synthesized and applied to the general internal medicine setting.

A Sensitive Approach to Managing Hypersensitivity Pneumonitis

Hypersensitivity pneumonitis (HP), also known as extrinsic allergic alveolitis, is an immunologically mediated disorder that typically presents as a case of interstitial lung disease (ILD) in response to any identified or unidentified antigen. We present a case of a 46-year-old female with HP, who presented with fever and shortness of breath. Although negative by real-time reverse transcription-polymerase chain reaction (RT-PCR), her condition was initially diagnosed as COVID-19 clinically as a result of anchoring bias due to similar symptoms and radiologic features presenting in the pandemic. A detailed further probing into history revealed the diagnosis of HP due to cat hair, and hence, was managed accordingly.

Pediatric hypersensitivity pneumonitis: literature update and proposal of a diagnostic algorithm

Hypersensitivity pneumonitis (HP) is a rare disease in childhood with the prevalence of 4 cases per 1 million children and an incidence of 2 cases per year. The average age of diagnosis at pediatric age is approximately 10 years. The pathogenesis of HP is characterized by an immunological reaction caused by recurrent exposure to triggering environmental agents (mostly bird antigens in children). The clinical picture of HP is complex and variable in children, often presenting in subacute forms with cough and exertion dyspnea. A diagnosis of HP should be considered in patients with an identified exposure to a triggering antigen, respiratory symptoms, and radiologic signs of interstitial lung disease. Blood tests and pulmonary function tests (PFT) support the diagnosis. Bronchoscopy (with bronchoalveolar lavage and tissue biopsy) may be needed in unclear cases. Antigen provocation test is rarely required. Of note, the persistence of symptoms despite various treatment regimens may support HP diagnosis. The avoidance of single/multiple triggers is crucial for effective treatment. No evidence- based guidelines for treatment are available; in particular, the role of systemic glucocorticoids in children is unclear. With adequate antigen avoidance, the prognosis in children with HP is generally favorable.

Hypersensitivity pneumonitis: Current concepts in pathogenesis, diagnosis, and treatment

Hypersensitivity pneumonitis is an immune-mediated interstitial lung disease caused by an aberrant response to an inhaled exposure, which results in mostly T cell-mediated inflammation, granuloma formation, and fibrosis in some cases. HP is diagnosed by exposure identification, HRCT findings of ground-glass opacities, centrilobular nodules, and mosaic attenuation, with traction bronchiectasis and honeycombing in fibrotic cases. Additional testing including serum IgG testing for the presence of antigen exposure, bronchoalveolar lavage lymphocytosis, and lung biopsy demonstrating granulomas, inflammation, and fibrosis, increases the diagnostic confidence. Treatment for HP includes avoidance of the implicated exposure, immunosuppression, and anti-fibrotic therapy in select cases. This narrative review presents the recent literature in the understanding of the immunopathological mechanisms, diagnosis, and treatment of HP.

MIXTURE of human expertise and deep learning-developing an explainable model for predicting pathological diagnosis and survival in patients with interstitial lung disease

Interstitial pneumonia is a heterogeneous disease with a progressive course and poor prognosis, at times even worse than those in the main cancer types. Histopathological examination is crucial for its diagnosis and estimation of prognosis. However, the evaluation strongly depends on the experience of pathologists, and the reproducibility of diagnosis is low. Herein, we propose MIXTURE (huMan-In-the-loop eXplainable artificial intelligence Through the Use of REcurrent training), an original method to develop deep learning models for extracting pathologically significant findings based on an expert pathologist's perspective with a small annotation effort. The procedure of MIXTURE consists of three steps as follows. First, we created feature extractors for tiles from whole slide images using self-supervised learning. The similar looking tiles were clustered based on the output features and then pathologists integrated the pathologically synonymous clusters. Using the integrated clusters as labeled data, deep learning models to classify the tiles into pathological findings were created by transfer-learning the feature extractors. We developed three models for different magnifications. Using these extracted findings, our model was able to predict the diagnosis of usual interstitial pneumonia, a finding suggestive of progressive disease, with high accuracy (AUC 0.90 in validation set and AUC 0.86 in test set). This high accuracy could not be achieved without the integration of findings by pathologists. The patients predicted as UIP had poorer prognosis (5-year overall survival [OS]: 55.4%) than those predicted as non-UIP (OS: 95.2%). The Cox proportional hazards model for each microscopic finding and prognosis pointed out dense fibrosis, fibroblastic foci, elastosis, and lymphocyte aggregation as independent risk factors. We suggest that MIXTURE may serve as a model approach to different diseases evaluated by medical imaging, including pathology and radiology, and be the prototype for explainable artificial intelligence that can collaborate with humans.

Antigen avoidance and outcome of nonfibrotic and fibrotic hypersensitivity pneumonitis

Background

Hypersensitivity pneumonitis (HP) is classified into nonfibrotic and fibrotic phenotypes. Patients with nonfibrotic HP often experience recurrence and develop fibrosis, whereas those with fibrotic HP have a poor prognosis. Although antigen avoidance has long been the first line of treatment for HP, its impact on prognosis has been poorly reported.

Methods

Medical records of 121 patients with HP diagnosed by new diagnostic criteria of American Thoracic Society/Japanese Respiratory Society/Asociación Latinoamericana del Tórax (ATS/JRS/ALAT) guidelines and treated at our institution in Saitama, Japan, were retrospectively analysed. HP was classified into nonfibrotic and fibrotic phenotypes and six HP subtypes: summer-type, bird-related, home-related and occupational HP, humidifier lung, and hot tub lung. Achievement of reduced exposure to inciting agents was divided into complete antigen avoidance (CAA) and incomplete antigen avoidance (IAA) by HP subtype.

Results

Of the 74 patients with nonfibrotic HP, 30 achieved CAA and experienced no recurrence or development of fibrosis. In the remaining 44 patients with IAA, 24 (54.5%) experienced recurrence and/or development of fibrosis. The all-cause 5-year mortality rate in the 47 patients with fibrotic HP was 47.8%. Negative prognostic factors of HP-related mortality in these patients were <50% lymphocytes in bronchoalveolar lavage (BAL) and honeycombing. Multivariate analysis showed a tendency for IAA to be related to poorer survival (hazard ratio 3.452, 95% CI 0.964–12.359, p=0.057).

Conclusions

In the patients with nonfibrotic HP, CAA resulted in no recurrence or development of fibrosis and longer survival. In the patients with fibrotic HP, <50% lymphocytes in BAL and honeycombing were negative prognostic factors for mortality.

Complete antigen avoidance reduces the recurrence and development of fibrosis in patients with nonfibrotic HP and may be related to longer survival in patients with fibrotic HPhttps://bit.ly/3E5EVLR

Occupational Hypersensitivity Pneumonitis in a Japanese Citrus Farmer

Hypersensitivity pneumonitis (HP) sometimes develops in people working in specific environments. We herein report a case of occupation-related HP in a citrus farmer in Japan. A 66-year-old man developed a fever, dyspnea, and general malaise in March after working near a trash dump filled with moldy tangerines. He presented with leukocytosis, bilateral lung opacities on chest radiographs, and intra-alveolar and interstitial lymphocytic inflammation with fibrotic change on a lung biopsy. His symptoms disappeared after admission and recurred on a revisit to the workplace. Fungal culture and a mycobiome analysis using next-generation sequencing suggested an association with exposure to Penicillium digitatum.

Questionnaires or Serum Immunoglobulin G Testing in the Diagnosis of Hypersensitivity Pneumonitis among Patients with Interstitial Lung Disease

Rationale: Hypersensitivity pneumonitis (HP) results from exposure to a variety of stimuli, which are challenging to identify. Questionnaires and serum immunoglobulin G (IgG) testing are methods to identify potentially causative exposures.Objectives: To perform a systematic review to determine the usefulness of questionnaires and serum IgG testing in identifying exposures that may have caused HP.Methods: This systematic review informed an international, multidisciplinary panel that developed a clinical practice guideline on the diagnosis of HP for the American Thoracic Society, Japanese Respiratory Society, and Asociación Latinoamericana del Tórax. MEDLINE, the Cochrane Library, and EMBASE were searched from January 1946 to October 2019 for studies that used a questionnaire or serum IgG testing to identify exposures that may have caused HP. The Grading of Recommendations, Assessment, Development, and Evaluation approach was used to appraise the quality of the evidence.Results: Searches identified 1,141 and 926 potentially relevant articles for questionnaires and serum IgG testing, respectively. The full texts of 32 and 49 articles, respectively, were reviewed. Two observational studies for questionnaires and 15 accuracy studies for serum IgG testing were selected. Questionnaires were better at detecting potentially relevant exposures than clinical history (100% vs. 26%; risk ratio [RR], 3.80; 95% confidence interval [95% CI], 1.79-8.06) and serum IgG testing (100% vs. 63%; RR, 1.58; 95% CI, 1.12-2.23) but did not differ from serum IgG testing plus bronchial challenge testing (59% vs. 65%; RR, 0.90; 95% CI, 0.65-1.24). Longer, detailed questionnaires were more likely to lead to identification of potential exposures. Only 70% of potential exposures identified by questionnaires were subsequently confirmed by environmental testing. Serum IgG testing distinguished HP from healthy exposed and unexposed control subjects with high sensitivity (90% and 92%, respectively) and high specificity (91% and 100%, respectively) but did not distinguish HP as effectively from interstitial lung diseases (ILDs; sensitivity of 83% and specificity of 68%).Conclusions: Using a questionnaire may help clinicians identify potentially relevant exposures when evaluating a patient with newly identified ILD for HP. Serum IgG testing may also lead to identification of potentially relevant exposures, but its usefulness for distinguishing HP from other types of ILD is poor.

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.

Sarcoidosis: Pitfalls and Challenging Mimickers

Sarcoidosis, a systemic granulomatous disease of unknown etiology, may mimic other conditions at presentation often resulting in delayed diagnosis. These conditions include infections, neoplasms, autoimmune, cardiovascular, and drug-induced diseases. This review highlights the most common sarcoidosis mimics that often lead to pitfalls in diagnosis and delay in appropriate treatment. Prior to invasive testing and initiating immunosuppressants (commonly corticosteroids), it is important to exclude sarcoid mimickers.

Hypersensitivity pneumonitis, allergic bronchopulmonary aspergillosis and other eosinophilic lung diseases

Hypersensitivity pneumonitis (HP) is traditionally classified into acute, subacute and chronic forms. A high index of suspicion and a detailed investigation into the patient's environment is the key to diagnosis and treatment of HP. Eosinophilic lung diseases can be broadly categorized as idiopathic (acute eosinophilic pneumonia, chronic eosinophilic pneumonia, eosinophilic granulomatosis with polyangiitis and hypereosinophilic syndromes), those with known cause (allergic bronchopulmonary aspergillosis, drugs, parasitic and non-parasitic infections), and those associated with other known lung diseases (asthma, interstitial lung diseases and lung cancers). A detailed review of drug intake, toxin exposures, and travel history is essential in the differential diagnosis of eosinophilic lung diseases.

Cytokine gene polymorphisms in Pigeon Breeder's Disease expression

BACKGROUND

Exaggerated immunological response to repeated inhalation of organic or chemical dusts may lead to Hypersensitivity Pneumonitis among sensitized individuals. Only a few exposed individuals became ill and disease expression pattern is highly variable which suggest that genetic factors may play a role.

AIM

To investigate interferon (IFN)-γ, tumour necrosis factor (TNF)-α, interleukin (IL)-6, transforming growth factor (TGF)-ß, and IL-10 gene polymorphisms in a cohort of pigeon breeder's disease (PBD) patients in comparison with exposed but healthy controls and the association with different patterns of disease.

METHODS

We evaluated 40 PBD patients and 70 exposed controls. IFN-γ, TNF-α, IL-6, TGF-ß, and IL-10 polymorphisms were determined by polymerase chain reaction-sequence specific primer amplification.

RESULTS

Polymorphism analysis of IFN-γ, TNF-α, IL-6, TGF-ß, and IL-10 genotypes and allele frequencies showed no differences between patients and controls. IFN-γ T/T genotype frequency was increased among patients with chronic presentation (RR=2.33, p=0.047) compared with those with acute/subacute presentation. Also, chronic presenting patients had an increased frequency of IFN-γ T allele (50% vs 22.5%, RR=1.76, p=0.011). No differences were found in TNF-α, IL-6, TGF-ß, and IL-10 genotypes neither allelic frequencies between both groups of patients. IL-6 C/C genotype was more frequent in patients who showed chronic evolution (RR=2.54, p=0.017), when comparing with patients with disease resolution.

CONCLUSION

IFN-γ T/T and the IL-6 C/C genotypes seem to play a role in HP expression due to avian exposure, as their frequencies are increased in chronic presentations or in those with chronic evolution one year after the initial diagnosis, respectively. (Sarcoidosis Vasc Diffuse Lung Dis 2020; 37 (3): e2020004).

Diagnosis of Hypersensitivity Pneumonitis in Adults. An Official ATS/JRS/ALAT Clinical Practice Guideline

Background: This guideline addresses the diagnosis of hypersensitivity pneumonitis (HP). It represents a collaborative effort among the American Thoracic Society, Japanese Respiratory Society, and Asociación Latinoamericana del Tórax.Methods: Systematic reviews were performed for six questions. The evidence was discussed, and then recommendations were formulated by a multidisciplinary committee of experts in the field of interstitial lung disease and HP using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) approach.Results: The guideline committee defined HP, and clinical, radiographic, and pathological features were described. HP was classified into nonfibrotic and fibrotic phenotypes. There was limited evidence that was directly applicable to all questions. The need for a thorough history and a validated questionnaire to identify potential exposures was agreed on. Serum IgG testing against potential antigens associated with HP was suggested to identify potential exposures. For patients with nonfibrotic HP, a recommendation was made in favor of obtaining bronchoalveolar lavage (BAL) fluid for lymphocyte cellular analysis, and suggestions for transbronchial lung biopsy and surgical lung biopsy were also made. For patients with fibrotic HP, suggestions were made in favor of obtaining BAL for lymphocyte cellular analysis, transbronchial lung cryobiopsy, and surgical lung biopsy. Diagnostic criteria were established, and a diagnostic algorithm was created by expert consensus. Knowledge gaps were identified as future research directions.Conclusions: The guideline committee developed a systematic approach to the diagnosis of HP. The approach should be reevaluated as new evidence accumulates.

Use of leflunomide in patients with chronic hypersensitivity pneumonitis

Background

Prednisone has been shown to reverse lung function declines in hypersensitivity pneumonitis patients without established fibrosis. Second line immunosuppressants like azathioprine and mycophenolate mofetil have a steroid sparing effect and improve DLCO. There is no published literature on the use of leflunomide in such patients.

Methods

We reviewed our experience with leflunomide for treatment of chronic hypersensitivity pneumonitis in 40 patients. We stratified patients according to the presence or absence of significant (> 20%) fibrosis. We studied the effect of leflunomide on FVC and DLCO trajectory and reported the changes at 12 months.

Results

Treatment with leflunomide tended to improve the estimated FVC slope from 0.18 ± 1.90% (SEM) of predicted per year to 4.62 ± 1.65% of predicted (NS, p = 0.118). It significantly improved the FVC at 12 months of treatment by 4.4% of predicted (p = 0.02). DLCO continued to increase at 1.45 ± 1.44% (SEM) of predicted per year. Non-fibrotic cHP patients had the largest gain in pulmonary function. Their FVC increased by 8.3% (p = 0.001) and DLCO by 4.8% (p = 0.011). Patients with fibrotic cHP did not improve. Leflunomide treatment was associated with significant gastrointestinal and other adverse effects leading 40% of patients to discontinue therapy. It had a significant steroid sparing effect with half the patients weaned off prednisone entirely.

Conclusions

Leflunomide appears to be a fairly well tolerated steroid sparing immunosuppressant that improves pulmonary function in cHP patients. It is most effective in patients without significant fibrosis.

Interstitial lung diseases in children

Interstitial lung disease (ILD) in children (chILD) is a heterogeneous group of rare respiratory disorders that are mostly chronic and associated with high morbidity and mortality. The pathogenesis of the various chILD is complex and the diseases share common features of inflammatory and fibrotic changes of the lung parenchyma that impair gas exchanges. The etiologies of chILD are numerous. In this review, we chose to classify them as ILD related to exposure/environment insults, ILD related to systemic and immunological diseases, ILD related to primary lung parenchyma dysfunctions and ILD specific to infancy. A growing part of the etiologic spectrum of chILD is being attributed to molecular defects. Currently, the main genetic mutations associated with chILD are identified in the surfactant genes SFTPA1, SFTPA2, SFTPB, SFTPC, ABCA3 and NKX2-1. Other genetic contributors include mutations in MARS, CSF2RA and CSF2RB in pulmonary alveolar proteinosis, and mutations in TMEM173 and COPA in specific auto-inflammatory forms of chILD. However, only few genotype-phenotype correlations could be identified so far. Herein, information is provided about the clinical presentation and the diagnosis approach of chILD. Despite improvements in patient management, the therapeutic strategies are still relying mostly on corticosteroids although specific therapies are emerging. Larger longitudinal cohorts of patients are being gathered through ongoing international collaborations to improve disease knowledge and targeted therapies. Thus, it is expected that children with ILD will be able to reach the adulthood transition in a better condition.

Current Diagnosis and Management of Hypersensitivity Pneumonitis

Hypersensitivity Pneumonitis (HP) one of the most common interstitial lung diseases (ILDs) is characterized by exposure to an inhaled inciting antigen that leads to a host immunologic reaction determining interstitial inflammation and architectural distortion. The underlying pathogenetic mechanisms are unclear. The absence of international shared diagnostic guidelines and the lack of a "gold-standard" test for HP combined with the presence of several clinical and radiologic overlapping features makes it particularly challenging to differentiate HP from other ILDs, also in expert contests. Radiology is playing a more crucial role in this process; recently the headcheese sign was recognized as a more specific for chronic-HP than the extensive mosaic attenuation. Several classification proposals and diagnostic models have been advanced by different groups, with no prospective validation. Therapeutic options for HP have been limited to antigen avoidance and immunosuppressant drugs over the last decades. Several questions about this condition remain unanswered and there is a need for more studies.

Epidemiology of Hypersensitivity Pneumonitis among an Insured Population in the United States: A Claims-based Cohort Analysis

RATIONALE

Hypersensitivity pneumonitis is a complex lung disease resulting from repeated inhalation of a variety of antigens. Limited data exist regarding its epidemiology.

OBJECTIVES

To describe the trends in the annual incidence and prevalence of hypersensitivity pneumonitis in the United States.

METHODS

We developed novel claims-based coding algorithms to identify hypersensitivity pneumonitis, chronic hypersensitivity pneumonitis, and fibrotic hypersensitivity pneumonitis cases using the 2004 to 2013 MarketScan Commercial and Medicare Supplemental healthcare claims databases. Algorithm validity and reliability were assessed with clinical data from National Jewish Health. We calculated yearly cumulative incidence and prevalence overall and by age. For the subgroup with vital status, Kaplan-Meier methods were used to analyze survival stratified by evidence of fibrosis.

RESULTS

We identified 7,498 cases that met our hypersensitivity pneumonitis definition over the 10-year study period, including 3,902 with chronic hypersensitivity pneumonitis and 1,852 with fibrotic hypersensitivity pneumonitis. On the basis of the clinical-radiological adjudication of the validation sample, 38 cases (95%) were confirmed as hypersensitivity pneumonitis. The mean age was 52 years, and 58% were women. The 1-year prevalence rates for hypersensitivity pneumonitis ranged from 1.67 to 2.71 per 100,000 persons, and 1-year cumulative incidence rates ranged from 1.28 to 1.94 per 100,000 persons. The prevalence increased with age, ranging from 0.95 per 100,000 among 0- to 9-year-olds to 11.2 per 100,000 among those aged 65 years and older. Between 56 and 68% of hypersensitivity pneumonitis cases in each year were classified as chronic hypersensitivity pneumonitis (prevalence, 0.91-1.70 per 100,000 persons; cumulative incidence, 0.63-1.08 per 100,000 persons). Fewer had fibrotic hypersensitivity pneumonitis (prevalence, 0.41-0.80 per 100,000 persons; cumulative incidence: 0.29-0.43 per 100,000 persons). Most cases (74%) were classified as unspecified hypersensitivity pneumonitis. Older age, male sex, and fibrosis were associated with higher mortality rates in unadjusted analyses.

CONCLUSIONS

Using U.S. administrative claims-based data, we developed an algorithm with a high sensitivity and specificity for hypersensitivity pneumonitis. Between 2004 and 2013, hypersensitivity pneumonitis was more common among women and those older than 65 years. Most cases were classified as chronic hypersensitivity pneumonitis. Approximately one-fourth met our criteria for fibrotic hypersensitivity pneumonitis, which was associated with a higher mortality rate.

[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.

Occupational Lung Diseases: Underreported Diagnosis in Radiological Practice

Underreporting of occupational lung diseases is a widespread problem in clinical practice. In Europe there is not a common regulation even for the recognition of occupational cancers. Furthermore epidemiologic data on occupational interstitial lung diseases, in general, is limited by no standardized diagnostic criteria, varied physician awareness and training, limitations inherent to the various data sources, and the long latency period. Therefore, to optimize the management of the patient with occupational pathology, the collaboration and skills of the multidisciplinary at the service of the patient, play a fundamental role. In particular, radiologists should give substance to a clinical suspicion on an anamnestic basis and at the same time should recognize patterns of illness that can lead to the emergence of stories of misunderstood exposures. This article aims to provide an overview of the main occupational lung diseases with attention to diagnostic possibilities of the different imaging techniques. The issue of the radiological error is investigated, providing tools to minimize it in the daily practice.

Chronic interstitial lung diseases in children: diagnosis approaches

Introduction: Children interstitial lung disease (chILD) is a heterogeneous group of rare respiratory disorders characterized by inflammatory and fibrotic changes of the lung parenchyma. They include ILD related to exposure/environment insults, ILD related to systemic diseases processes, ILD related to primary lung parenchyma dysfunctions and ILD specific to infancy. Areas covered: This review provides an update on chILD pathophysiology and diagnosis approaches in immunocompetent children. It includes current information on genetic causes. Expert commentary: ChILD covers a large spectrum of entities with heterogeneous disease expression. Various classifications have been reported, but none of them seems completely satisfactory. Recently, progress in molecular genetics has allowed identifying some genetic contributors, with, so far, a lack of correlations between gene disorders and disease expression. Despite improvements in patient management, chILD prognosis is still burdened by significant morbidity and mortality. Ongoing international collaborations will allow gathering larger longitudinal cohorts of patients to improve disease knowledge and personalized care. The overall goal is to help the children with ILD to reach the adulthood transition in a better condition, and to structure genetic counseling for their family.

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.

Stop Being So Sensitive: An Exceptionally Rare Report of Ustekinumab-Induced Sub-acute Hypersensitivity Pneumonitis

Hypersensitivity pneumonitis (HSP) is a rare syndrome characterised by granulomatous inflammatory lung disease due to repeated sensitisation from a specific antigen. We present the case of a 61-year old male veteran with a history of nodular eczema who presented with 2 weeks of progressive dyspnoea on exertion and pleuritic chest pain. The patient was started on ustekinumab 5 weeks prior to presentation. Initial workup revealed ground-glass opacities on computed tomography (CT) scan of the chest. Cardiac workup was unrevealing with a normal myocardial perfusion stress test. The patient was started on inhaled corticosteroids and albuterol for reactive airway disease. Due to the persistence of symptoms despite treatment, the patient underwent bronchoscopy with bronchoalveolar lavage (BAL), transbronchial biopsy and endobronchial ultrasound-guided biopsy (EBUS). Bronchoscopy showed normal appearing airways of both right and left lungs. The BAL was remarkable for chronic inflammation and pulmonary macrophages. The BAL cell count differential was 1% granulocytes, 50% lymphocytes, 17% eosinophils and 32 mononuclear cells. The pathology from the mediastinal lymph nodes showed reactive inflammatory cells and no malignancy. The pathology from the transbronchial biopsy of the anterior basilar segment of the right lower lobe showed organising pneumonia with occasional ill-defined granulomas that stained negative for Acid Fast Bacilli (AFB) and Grocott's methenamine (GMS) appeared to be consistent with hypersensitivity pneumonitis. Based on the pathological diagnosis of HSP, the patient was managed with discontinuation of ustekinumab, with subsequent improvement of his symptoms. To our knowledge, this is the first report suggesting ustekinumab, like other biological therapies, has the potential to cause HSP.

Pulmonary and sinus fungal diseases in non-immunocompromised patients

The human respiratory tract is exposed daily to airborne fungi, fungal enzymes, and secondary metabolites. The endemic fungi Histoplasma capsulatum, Coccidioides spp, Blastomyces dermatitidis, and Paracoccidioides brasiliensis, and occasionally Aspergillus fumigatus, are primary pulmonary pathogens of otherwise healthy people. Such infections resolve in most people, and only a few infections lead to disease. However, many fungi are directly allergenic by colonising the respiratory tract or indirectly through contact with cell wall constituents and proteases, causing or exacerbating allergic disease. Increasing evidence implicates high indoor fungal exposures as a precipitant of asthma in children and in worsening asthma symptoms. Lung or airways infection by endemic fungi or aspergillus can be diagnosed with respiratory sample culture or serum IgG testing. Sputum, induced sputum, or bronchial specimens are all suitable specimens for detecting fungi; microscopy, fungal culture, galactomannan antigen, and aspergillus PCR are useful tests. Antifungal treatment is indicated in almost all patients with chronic cavitary pulmonary infections, chronic invasive and granulomatous rhinosinusitis, and aspergillus bronchitis. Most patients with fungal asthma benefit from antifungal therapy. Adverse reactions to oral azoles, drug interactions, and azole resistance in Aspergillus spp limit therapy. Environmental exposures, genetic factors, and structural pulmonary risk factors probably underlie disease but are poorly understood.

Hypersensitivity Pneumonitis Due to Metalworking Fluid Aerosols

PURPOSE OF REVIEW

This review summarises the clinical knowledge of hypersensitivity pneumonitis in workers exposed to aerosols of metalworking fluid, reviewing published outbreaks and clinical cases.

RECENT FINDINGS

Metalworking fluid exposure has become the commonest recognised cause of occupational hypersensitivity pneumonitis, having been rare before 2000. There are many possible agents in the metalworking fluid which may be the cause of disease including bacteria, mycobacteria, fungae, biocides, emulsifiers, reodorants and dissolved chrome and cobalt. Causes are likely to be different in different outbreaks. Mycobacteria growing in the metalworking fluid have generated immune responses in some workers, but their role in disease causation is not yet established. Many outbreaks have been identified in large workplaces using common sumps. It is not possible to prevent microbial contamination of metalworking fluids in use. Disease prevention should focus on stopping inhalation of aerosols, particularly by re-engineering to remove recirculation.

Hypersensitivity pneumonitis: an overlooked cause of cough and dyspnea

Hypersensitivity pneumonitis (HP) is an immune-mediated pulmonary disorder involving inflammation of the lung interstitium, terminal bronchioles, and alveoli caused by the immune response to the inhalation of an offending environmental airborne agent. It can manifest as exertional dyspnea, fatigue, weight loss, and progressive respiratory failure if left untreated. Because of its protean features, it can be misdiagnosed as other common obstructive lung conditions such as asthma. If triggers are not avoided, it can progress to irreversible pulmonary fibrosis. In this article, we present the case of a 51-year-old male who presented to our hospital with recurrent bouts of dyspnea and cough, initially diagnosed as an asthma exacerbation. He received a final diagnosis of HP after investigation of his workplace revealed airborne spores and surface molds from multiple fungal species, serology revealed eosinophilia, and computed tomography showed bronchiectasis. Avoidance of occupational exposure resulted in significant improvement of his respiratory symptoms after two months.

Abbreviations: HP: Hypersensitivity pneumonitis

Chronic hypersensitivity pneumonitis: identification of key prognostic determinants using automated CT analysis

Background

Chronic hypersensitivity pneumonitis (CHP) has a variable disease course. Computer analysis of CT features was used to identify a subset of CHP patients with an outcome similar to patients with idiopathic pulmonary fibrosis (IPF).

Methods

Consecutive patients with a multi-disciplinary team diagnosis of CHP (n = 116) had pulmonary function tests (FEV1, FVC, DLco, Kco, and a composite physiologic index [CPI]) and CT variables predictive of mortality evaluated by analysing visual and computer-based (CALIPER) parenchymal features: total interstitial lung disease (ILD) extent, honeycombing, reticular pattern, ground glass opacities, pulmonary vessel volume (PVV), emphysema, and traction bronchiectasis. Mean survival was compared between both CHP and IPF patients (n = 185).

Results

In CHP, visual/CALIPER measures of reticular pattern, honeycombing, visual traction bronchiectasis, and CALIPER ILD extent were predictive of mortality (p < 0 · 05) on univariate analysis. PVV was strongly predictive of mortality on univariate (p < 0 · 0001) and multivariate analysis independent of age, gender and disease severity (represented by the CPI [p < 0 · 01]). CHP patients with a PVV threshold >6 · 5% of the lung had a mean survival (35 · 3 ± 6 · 1 months; n = 20/116 [17%]) and rate of disease progression that closely matched IPF patients (38 · 4 ± 2 · 2 months; n = 185).

Conclusions

Pulmonary vessel volume can identify CHP patients at risk of aggressive disease and a poor IPF-like prognosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12890-017-0418-2) contains supplementary material, which is available to authorized users.

Utility of precipitating antibody testing in the diagnostic evaluation of chronic hypersensitivity pneumonia

Background: Chronic hypersensitivity pneumonitis (HP), in its progressive fibrotic form, is difficult to distinguish from other fibrosing interstitial lung diseases (ILD), particularly idiopathic pulmonary fibrosis (IPF) and non-specific interstitial pneumonia (NSIP). The role of serum precipitating antibodies in the diagnosis of fibrosing ILD has not been discussed in recent clinical practice guidelines. Objectives: The aim of this study is to assess the role of precipitins in the diagnosis of non pre-selected cases of fibrosing ILD. Methods: Clinical records of 108 consecutive patients referred for presumptive fibrosing ILD to our institution were retrospectively assessed for exposure history, serum precipitins, other diagnostic examinations, and multidisciplinary diagnosis (MDD). Their high resolution computed tomography (HRCT) images were blindly and prospectively re-assessed. We estimated sensitivity and specificity of precipitins against MDD and, to account for incorporation bias, we used two composite reference standards (CRSs), having exposure history and HRCT as component tests. Results: Definitive diagnosis achieved through MDD were chronic HP (17% of cases), NSIP (42%), IPF (18%) and others (23%). For serum precipitins, we estimated a sensitivity of 72% and a specificity of 68% using MDD as the reference standard. Sensitivity against the AND-CRS was 55%, while specificity against the OR-CRS was 61%. On the basis of this results, we can expect true sensitivity of precipitins lying between 55 and 72% and specificity between 61 and 68%. Conclusions:Serum precipitating antibodies did not result as having a relevant role in the diagnostic approach to chronic HP (Sarcoidosis Vasc Diffuse Lung Dis 2017; 34: 149-155).

Clinical and molecular features of rapidly progressive chronic hypersensitivity pneumonitis

Background: Chronic hypersensitivity pneumonitis (CHP) is characterized by varying degrees of inflammation and fibrosis of the lungs caused by a variety of inhaled antigens. Despite extensive efforts to minimize exposure to the antigens, patients with CHP sometimes experience rapid deterioration of their pulmonary functions, resulting in death within a few years. Objectives: This study aimed to define clearly the clinical and molecular features of patients with rapidly progressive CHP. Methods: Annual decline in pulmonary functions and its association with clinical variables was evaluated in 43 patients with CHP. The RNA from frozen lung specimens of nine patients with rapidly progressive CHP and normal control subjects was profiled using Illumina HumanWG-6 v3 Expression BeadChips, and an Ingenuity Pathway Analysis was performed to identify the altered functional and canonical signaling pathways. Results: Patients with more than 10% annual decline in forced vital capacity and those with more than 15% annual decline in diffusion capacity for carbon monoxide showed significantly poor overall survival rates (p=0.002 and p=0.001, respectively). According to the gene expression analysis, 160 genes, including cystatin SN (CST1), ephrin-A2 (EFNA2), and wingless-type MMTV integration site family, member 7B (WNT7B) were upregulated, and pathways related to inflammatory responses and autoimmune diseases were differentially expressed. Conclusion: Greater annual decline in pulmonary function can predict poorer prognosis of patients with CHP. Genes and pathways related to inflammatory responses and autoimmune diseases have potential roles in the pathogenesis of rapidly progressive CHP, suggesting their potential as diagnostic biomarkers and/or therapeutic targets. (Sarcoidosis Vasc Diffuse Lung Dis 2017; 34: 48-57).

Hypersensitivity pneumonitis: a complex lung disease

Hypersensitivity pneumonitis (HP), also called extrinsic allergic alveolitis, is a respiratory syndrome involving the lung parenchyma and specifically the alveoli, terminal bronchioli, and alveolar interstitium, due to a delayed allergic reaction. Such reaction is secondary to a repeated and prolonged inhalation of different types of organic dusts or other substances to which the patient is sensitized and hyper responsive, primarily consisting of organic dusts of animal or vegetable origin, more rarely from chemicals. The prevalence of HP is difficult to evaluate because of uncertainties in detection and misdiagnosis and lacking of widely accepted diagnostic criteria, and varies considerably depending on disease definition, diagnostic methods, exposure modalities, geographical conditions, agricultural and industrial practices, and host risk factors. HP can be caused by multiple agents that are present in work places and in the home, such as microbes, animal and plant proteins, organic and inorganic chemicals. The number of environment, settings and causative agents is increasing over time. From the clinical point of view HP can be divided in acute/subacute and chronic, depending on the intensity and frequency of exposure to causative antigens. The mainstay in managing HP is the avoidance of the causative antigen, though the complete removal is not always possible due to the difficulties to identify the agent or because its avoidance may lead to major changes in life style or occupational settings. HP is a complex syndrome that needs urgently for more stringent and selective diagnostic criteria and validation, including wider panels of IgG, and a closer collaboration with occupational physicians, as part of a multidisciplinary expertise.

Chronic hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HSP) is a common interstitial lung disease resulting from inhalation of a large variety of antigens by susceptible individuals. The disease is best classified as acute and chronic. Chronic HSP can be fibrosing or not. Fibrotic HSP has a large differential diagnosis and has a worse prognosis. The most common etiologies for HSP are reviewed. Diagnostic criteria are proposed for both chronic forms based on exposure, lung auscultation, lung function tests, HRCT findings, bronchoalveolar lavage, and biopsies. Treatment options are limited, but lung transplantation results in greater survival in comparison to idiopathic pulmonary fibrosis. Randomized trials with new antifibrotic agents are necessary.

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.

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.

Chronic hypersensitivity pneumonitis: important considerations in the work-up of this fibrotic lung disease

PURPOSE OF REVIEW

Chronic hypersensitivity pneumonitis is increasingly recognized as an important mimic of other fibrotic lung diseases. This review will summarize recent data regarding the importance and difficulty of determining causative exposures both for accurate diagnosis and prognosis, and describe the expanded pathologic spectrum of the disease, the effects of fibrosis on prognosis and challenges in the diagnostic evaluation.

RECENT FINDINGS

Several recent publications show the potential pathologic patterns induced by chronic hypersensitivity pneumonitis are broader than the classic triad of bronchiolitis, interstitial infiltrates and granulomas. Other pathologic patterns include nonspecific interstitial pneumonia, usual interstitial pneumonia, organizing pneumonia, bronchiolitis and airway centric fibrosis. Detecting a causative antigen in fibrotic hypersensitivity pneumonitis is challenging but critically important both for accurate diagnosis and improved prognosis. The prognosis in hypersensitivity pneumonitis worsens in the presence of fibrosis, but it remains significantly better than idiopathic pulmonary fibrosis.

SUMMARY

Hypersensitivity pneumonitis is increasingly recognized as an important cause of fibrotic interstitial lung disease. Hypersensitivity pneumonitis demonstrates a remarkable tendency to mimic other idiopathic interstitial pneumonias. A detailed exposure history remains a cornerstone of diagnosis and management.

Pitfalls in diagnosis and management of hypersensitivity pneumonitis

PURPOSE OF REVIEW

Hypersensitivity pneumonitis is a complex syndrome characterized by a combination of inflammation and fibrosis located in both the airways and the lung parenchyma. Both diagnosis and treatment are a real challenge for physicians. This review will focus on recent developments in this emerging field; furthermore, we will emphasize major gaps in the current knowledge, to stimulate further research in this field.

RECENT FINDINGS

The main diagnostic issue is not to miss the entity as the clinical presentation is extremely variable even as the nature of the causal antigen. This article provides an overview of current ways to uncover possible causes of hypersensitivity pneumonitis. A problem of another kind is treatment of this disorder. Crucial in treatment is antigen avoidance, often in combination with immunosuppressive agents. The treatment of acute forms is rather straightforward, but the biggest endeavour, however, is treatment of chronic forms of hypersensitivity pneumonitis, which not always respond to immunosuppressive agents. Therefore, new initiatives should be taken in order to help clinicians in making a proper diagnosis and develop more efficacious treatment especially for patients suffering from chronic hypersensitivity pneumonitis.

SUMMARY

Diagnosis and treatment of hypersensitivity pneumonitis remain a real challenge; this article provides an overview of our current understanding and points out new opportunities for further research.

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.

Hypersensitivity pneumonitis and antigen identification--An alternate approach

OBJECTIVES

Identification of the causal antigen for patients with hypersensitivity pneumonitis (HP) is challenging in a standard clinical setting. The purpose of this pilot study was to determine whether it was possible to evaluate the home/workplace of patients, and identify the causal antigen.

METHODS

Using a case-control study design we compared the presence of antibody to antigen collected in the environment of individuals with HP and controls consisting of family members/co-workers. Based on patient interviews, homes/workplaces were evaluated and suspected sources of antigen collected for use in immunoassays.

RESULTS

Nineteen individuals with HP participated with 15 classified as having fibrotic disease. Up to 54 bulk samples were collected from each patient's environment, with multiple isolates (antigens) cultured from each. Of the seven individuals who tested positive to one or more environmental samples, three had a positive response to more than 1 antigen from the environmental sample (range 1-9). Twelve individuals tested positive to antigen(s) on a standard panel, with only one overlapping with the antigen from the home/workplace sample. A significant association existed between results of interviews/site evaluations, and ability to collect antigen eliciting a positive response (p < 0.001).

CONCLUSION

Antigen identification was successful for patients with 'active' disease. Antigens for which patients test positive on standard panels may not be present in their environment. One benefit to patient-centered testing is the ability to develop recommendations specific to their environment. As most individuals tested positive for >1 antigen, further investigation is warranted to determine the actual antigen responsible for disease.