Clinicopathological features of chronic hypersensitivity pneumonitis

Successful diagnosis of humidifier lung by individual provocation test to a responsible environment, a case report

A 52-year-old woman presented with repeating episodes of pneumonia which spontaneously resolved after hospitalization. Hypersensitivity pneumonitis was suspected, but the causative antigen was not determined whether the parakeets she kept or the humidifier she owned was causative exposure. To identify which exposure is culprit, individual provocation test to a responsible environment was sequentially conducted. First, a home-returning provocation test to the parakeet was negative. Contrarily, the humidifier provocation test to her own humidifier was positive for symptoms, radiological changes, and inflammatory responses in blood test. Finally, she was diagnosed as having humidifier lung. When several antigens are suspected to be the causative agents for hypersensitivity pneumonitis, a step-by-step provocation tests is useful.

Disease pathology in fibrotic interstitial lung disease: is it all about usual interstitial pneumonia?

The interstitial pneumonias comprise a diverse group of diseases that are typically defined by their cause (either idiopathic or non-idiopathic) and their distinct histopathological features, for which radiology, in the form of high-resolution CT, is often used as a surrogate. One trend, fuelled by the failure of conventional therapies in a subset of patients and the broad-spectrum use of antifibrotic therapies, has been the focus on the progressive fibrosing phenotype of interstitial lung disease. The histological pattern, known as usual interstitial pneumonia, is the archetype of progressive fibrosis. However, it is clear that progressive fibrosis is not exclusive to this histological entity. Techniques including immunohistochemistry and single-cell RNA sequencing are providing pathogenetic insights and, if integrated with traditional histopathology, are likely to have an effect on the pathological classification of interstitial lung disease. This review, which focuses on the histopathology of interstitial lung disease and its relationship with progressive fibrosis, asks the question: is it all about usual interstitial pneumonia?

Role of Krebs von den Lungen-6 (KL-6) in Assessing Hypersensitivity Pneumonitis

Background

Hypersensitivity pneumonitis (HP) is an increasingly recognized form of diffuse parenchymal lung disease. Krebs von den Lungen-6 (KL-6) is now classified as a human MUC1 mucin protein, and regenerating type II pneumocytes are the primary cellular source of KL-6/MUC1 in the affected lungs of patients with interstitial lung diseases (ILD). Serum KL-6/MUC1 levels have been demonstrated to be useful for the evaluation of various ILD. To determine the role of circulating KL-6 in evaluating the disease activity and management of HP.

Methods

An observational cross-sectional study was conducted on 51 patients with HP and 20 healthy controls. Serum KL-6 levels were measured in both groups. Patients were further assessed based on chest high-resolution computed tomography (HRCT), pulmonary function test, 6-minute walk test, echocardiography, bronchioalveolar lavage, and/or transbronchial biopsy. Patients were divided into the fibrotic and non-fibrotic groups according to the HRCT findings.

Results

The median serum KL-6 levels were significantly higher in HP patients as compared to the control group. The median serum KL-6 levels were found to be higher in the non-fibrotic HP group (1,900 IU/mL) as compared to the fibrotic group (1,200 IU/mL). There was a significant inverse correlation between serum KL-6 serum level and the dose of steroids as well as the duration of steroid therapy.

Conclusion

The presence of higher KL-6 levels in the non-fibrotic HP group implies its enhanced production by regenerating pneumocytes in response to alveolar injury. The significant association between serum KL-6 levels and the dose and the duration of steroid therapy emphasizes the significant role of steroids in the stabilization of the disease.

Antigen avoidance in people with hypersensitivity pneumonitis: A scoping review

BACKGROUND

Antigen avoidance (AA) is essential for people with hypersensitivity pneumonitis (HP). An intervention programme to promote continuous AA in people with HP will be the focus of future research.

OBJECTIVES

We systematically analysed the AA behaviour of people with HP, interventions of health-care providers to promote AA behaviour, clinical outcomes after AA, and evaluation methods after AA.

METHODS

We conducted a scoping review using six online databases and manual searches. Papers written in English or Japanese that reported cases on AA were selected. The extracted data were classified qualitatively.

RESULTS

In total 205 cases included in 109 eligible papers were examined.

CONCLUSIONS

This review clarified the fundamental evidence of AA in people with HP. These people required the continuous support of health-care providers to continue appropriate AA. This review highlighted four aspects that require further research to design interventions for promoting effective and continuous AA in people with HP.

BAL and serum multiplex lipid profiling in idiopathic pulmonary fibrosis and fibrotic hypersensitivity pneumonitis

BACKGROUND

Differential diagnosis between IPF and fibrotic HP (fHP) can be challenging: these two ILDs share many common features but call for different therapeutic approaches. In the present study, differential lipid mediator profiles were analysed by a new method in BAL and serum from HP and IPF patients.

MATERIALS AND METHODS

76 patients were enrolled retrospectively in the study. Median age (IQR) was 67 years (51-74); 63% were males, 30 had fHP and 46 had IPF. Serum and BAL samples were collected at initial diagnosis. For quantification of serum and BAL lipid mediators was used bead-based multiplex LEGENDPlex™ analysis (Biolegend).

RESULTS

Serum Apo A1 levels were significantly higher in IPF than fHP patients (p = 0.314); indeed, serum levels of CCL2 and Apo C3 were lower in HP than in IPF patients (p = 0.013 and p = 0.041, respectively). BAL concentrations of Apo A1, adipsin, Apo C3 and APN were significantly lower in IPF than in fHP patients (p < 0.0001, p < 0.0001, p = 0.007 and p = 0.023, respectively). In the logistic regression, IPF was tested as dependent variable. Serum levels of Apo A1, CCL2 and Apo C3 were tested as independent variables and ROC curve analysis of model performance showed AUC 93% (p < 0.0001); on the other hand, BAL concentrations of Apo A1, adipsin, Apo C3 and APN showed AUC 81% (p < 0.0001).

DISCUSSION

Lipid biomarkers evaluated in BAL in our study confirm the hypothesis that fHP and IPF have different lung fibrosis phenotypes. The former is a post-inflammatory cell-regulated ILD and the second is more related to tissue remodeling and repair.

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.

Multiplex protein profiling of bronchoalveolar lavage in idiopathic pulmonary fibrosis and hypersensitivity pneumonitis

CONTEXT:

Idiopathic pulmonary fibrosis (IPF) and chronic hypersensitivity pneumonitis (HP) are diffuse parenchymal lung diseases characterized by a mixture of inflammation and fibrosis, leading to lung destruction and finally death.

AIMS:

The aim of this study was to compare different pathophysiological mechanisms, such as angiogenesis, coagulation, fibrosis, tissue repair, inflammation, epithelial damage, oxidative stress, and matrix remodeling, in both disorders using bronchoalveolar lavage (BAL).

METHODS:

At diagnosis, patients underwent bronchoscopy with BAL and were divided into three groups: Control (n = 10), HP (n = 11), and IPF (n = 11), based on multidisciplinary approach (clinical examination, radiology, and histology): Multiplex searchlight technology was used to analyze 25 proteins representative for different pathophysiological processes: Eotaxin, basic fibroblast growth factor (FGFb), fibronectin, hepatocyte growth factor (HGF), interleukine (IL)-8, IL-12p40, IL-17, IL-23, monocyte chemotactic protein (MCP-1), macrophage-derived chemokine (MDC), myeloperoxidase (MPO), matrix metalloproteinase (MMP)-8, MMP-9, active plasminogen activating inhibitor 1 (PAI-1), pulmonary activation regulated chemokine (PARC), placental growth factor (PlGF), protein-C, receptor for advanced glycation end products (RAGE), regulated on activation normal T cells expressed and secreted (RANTES), surfactant protein-C (SP-C), transforming growth factor-β1 (TGF-β1), tissue inhibitor of metalloproteinase-1 (TIMP-1), tissue factor, thymic stromal lymphopoietin (TSLP), and vascular endothelial growth factor (VEGF).

RESULTS:

All patients suffered from decreased pulmonary function and abnormal BAL cell differential compared with control. Protein levels were increased in both IPF and HP for MMP-8 (P = 0.022), MMP-9 (P = 0.0020), MCP-1 (P = 0.0006), MDC (P = 0.0048), IL-8 (P = 0.013), MPO (P = 0.019), and protein-C (P = 0.0087), whereas VEGF was decreased (P = 0.0003) compared with control. HGF was upregulated in HP (P = 0.0089) and active PAI-1 was upregulated (P = 0.019) in IPF compared with control. Differences in expression between IPF and HP were observed for IL-12p40 (P = 0.0093) and TGF-β1 (P = 0.0045).

CONCLUSIONS:

Using BAL, we demonstrated not only expected similarities but also important differences in both disorders, many related to the innate immunity. These findings provide new clues for further research in both disorders.

Hypersensitivity pneumonia: role of surgical lung biopsy

Lung biopsy often plays a key role in identifying patients with hypersensitivity pneumonia, especially in the absence of a typical history. A 69-year-old woman with a 2-year history of unexplained dyspnea on exertion underwent surgical lung biopsy for diagnosis of diffuse lung disease thought to represent idiopathic pulmonary fibrosis. Her biopsy showed honeycomb change and fibroblast foci suggestive of usual interstitial pneumonia, but also showed areas of cellular interstitial pneumonia with chronic bronchiolitis and a pattern of granulomatous inflammation typical of hypersensitivity pneumonia. The classic features of hypersensitivity pneumonia in surgical lung biopsy are emphasized, including a bronchiolocentric cellular interstitial pneumonia, chronic bronchiolitis, and poorly formed nonnecrotizing granulomas. As illustrated in our patient, sometimes subtle histologic clues are key in separating hypersensitivity pneumonia from usual interstitial pneumonia and other forms of idiopathic interstitial pneumonia. Making the distinction is important given differences in treatment strategies and natural history.

Hypersensitivity pneumonia: the role of lung biopsy in diagnosis and management

Hypersensitivity pneumonia is a form of diffuse interstitial lung disease resulting from sensitization to an inhaled antigen. Clinical and radiological features are relatively nonspecific, overlapping significantly with other forms of diffuse interstitial lung disease. Establishing the diagnosis in the absence of lung biopsy is challenging and is heavily dependent on being able to identify a specific antigenic exposure. Lung biopsy is especially important in diagnosing hypersensitivity pneumonia in patients for whom no incriminating exposure has been elucidated. Surgical lung biopsies show a classical combination of findings in the majority of patients, which include an airway-centered, variably cellular chronic interstitial pneumonia, a lymphocyte-rich chronic bronchiolitis, and poorly formed non-necrotizing granulomas distributed mainly within the peribronchiolar interstitium. The bronchiolitis may include variable degrees of peribronchiolar fibrosis and hyperplasia of the bronchiolar epithelium ('peribronchiolar metaplasia'), a characteristic but a nonspecific finding. In some patients, granulomatous inflammation may be lacking, resulting in a histological appearance resembling nonspecific interstitial pneumonia. Late-stage fibrotic hypersensitivity pneumonia results in clinical, radiological, and histological findings that closely mimic usual interstitial pneumonia. The presence of established collagen fibrosis, especially when associated with architectural distortion in the form of honeycomb change, is associated with shorter survivals.

Subacute and chronic hypersensitivity pneumonitis: histopathological patterns and survival

BACKGROUND

In hypersensitivity pneumonitis (HP), survival can be predicted on the basis of the severity of fibrosis in surgical lung biopsy, but few data are available on the influence of clinical, functional, tomographic and histologic findings on prognosis.

OBJECTIVES

To describe the impact on survival of clinical data, histological patterns, and HRCT findings in subacute/chronic HP.

METHODS

A retrospective analysis of 103 patients diagnosed with HP submitted to surgical lung biopsy. Chronic HP was characterized by HRCT findings indicative of fibrosis (n=76).

RESULTS

The most relevant exposures were to molds and birds. Lung biopsies revealed typical HP with granulomas in 46 patients, bronchiolocentric interstitial pneumonia in 27, and non-specific interstitial pneumonia (NSIP) in 16. By univariate analysis, several findings were predictors of mortality: older age, male sex, velcro crackles, higher FEV(1)/FVC ratio, lower oxygen saturation during exercise, and absence of mosaic pattern/air trapping and presence of fibrosis on HRCT. By multivariate analysis, remained significant: age (p=0.007), oxygen saturation during exercise (p=0.003), and mosaic pattern/air trapping on HRCT (p=0.004). Patients with NSIP had a greater survival than did those with typical histology and those with bronchiolocentric pneumonia (p=0.033).

CONCLUSIONS

A wide range of histological features are found in HP. Typical findings are seen in 45% of cases. Other common patterns are NSIP and centriacinar lesions. Survival is better in patients with NSIP and worse in those with older age, desaturation during exercise, and absence of mosaic pattern/air trapping on HRCT.

Pathologic patterns and survival in chronic hypersensitivity pneumonitis

The objective of the study was to examine the relationship of pathologic pattern and prognosis in hypersensitivity pneumonitis (HP). We analyzed 24 cases of subacute (cellular, nonfibrotic) and 25 cases of chronic (fibrotic) HP. Nineteen (79%) of the subacute cases showed a pattern of bronchiolocentric interstitial pneumonia and 5 (21%) a pattern mimicking cellular nonspecific interstitial pneumonia (NSIP). Giant cells or granulomas or Schaumann bodies were present in 19 cases (79%). Eighteen (72%) chronic cases showed a pattern resembling usual interstitial pneumonia (UIP), but, in most cases, with more peribronchiolar fibrosis than one would expect in UIP. Three fibrotic cases (12%) had only peribronchiolar fibrosis, whereas 4 (16%) resembled fibrotic NSIP. Giant cells or granulomas or Schaumann bodies were present in 22 (88%) cases. Areas of subacute HP were present in 12 cases with a UIP-like pattern. Only 2 UIP-like cases could not be morphologically distinguished from idiopathic UIP. The median survival for patients who had no fibrosis was 22.4 years; for patients with a fibrotic NSIP pattern was 2.1 years; and for those with a UIP-like pattern 2.8 years (not statistically different). Patients with a pattern of only peribronchiolar fibrosis had a median survival of 11.3 years. These data confirm that the presence of fibrosis is associated with a generally poor prognosis in patients with HP, and suggest that pure peribronchiolar fibrosis may portend a longer survival than does a UIP-like or fibrotic NSIP-like pattern of fibrosis. Most cases of chronic HP have distinctive pathologic features, but a small percentage of cases cannot be pathologically distinguished from UIP.

Histopathologic analysis of sixteen autopsy cases of chronic hypersensitivity pneumonitis and comparison with idiopathic pulmonary fibrosis/usual interstitial pneumonia

Hypersensitivity pneumonitis (HP) is an interstitial lung disease caused by the inhalation of organic substances and certain inorganic chemicals. The histopathologic features of chronic HP (CHP) have not been studied extensively. We examined the pathologic characteristics of 16 autopsy cases of clinically confirmed CHP and compared them with 11 cases of idiopathic pulmonary fibrosis/usual interstitial pneumonia (IPF/UIP). To clarify the exact intralobular location of the fibrotic lesions, we conducted 3-dimensional reconstruction of fibrosis of CHP and IPF/UIP. Granuloma was not detected in any CHP case. Similar to IPF/UIP, honeycombing lesions were found dominantly in the lower lobes in most CHP cases; upper lobe dominance and asymmetrical distribution of honeycomb lesions were more frequent in CHP than in IPF/UIP. In all lungs affected by CHP, centrilobular fibrosis was outstanding, often connecting to the perilobular areas in the appearance of "bridging fibrosis," which was clearly demonstrated by 3-dimensional imaging. Centrilobular and bridging fibrosis were significantly more conspicuous in CHP than IPF/UIP; however, considerable overlap was found. It is important to thoroughly explore the possibility of antigen exposure in cases of lungs with UIP with centrilobular fibrosis to discriminate CHP from IPF/UIP.

Pathology of hypersensitivity pneumonitis

PURPOSE OF REVIEW

Hypersensitity pneumonitis, caused by inhalation of various antigens, is characterized by interstitial mononuclear cell infiltration, nonnecrotizing granulomas, cellular bronchiolitis, and fibrosis. The pathological picture of chronic hypersensitivity pneumonitis is, however, complicated; it is sometimes difficult to differentiate chronic hypersensitivity pneumonitis from idiopathic pulmonary fibrosis/usual interstitial pneumonia, nonspecific interstitial pneumonia, and connective-tissue-related lung disease. The clinical, radiological, and pathological features of chronic hypersensitivity pneumonitis have recently been described. This study reviews the previously reported information and provides new insights into the pathological features of chronic hypersensitivity pneumonitis.

RECENT FINDINGS

The pathological features of chronic hypersensitivity pneumonitis comprise overlapping usual interstitial pneumonia-like pattern with subpleural patchy fibrosis, alternating normal alveoli and fibroblastic foci, a nonspecific interstitial pneumonia-like pattern, and centrilobular fibrosis. In contrast to pathological features of acute and subacute hypersensitivity pneumonitis, epithelioid cell granulomas are sparse or absent, but giant cells are seen in the interstitium. Bridging fibrosis between peribronchiolar area and perilobular areas is an outstanding feature of chronic hypersensitivity pneumonitis. Autopsy cases of chronic hypersensitivity pneumonitis have demonstrated not only upper lobe contraction but also lower lobe contraction, mimicking usual interstitial pneumonia pattern and diffuse alveolar damage.

SUMMARY

The present review focuses on the pathological features of chronic hypersensitivity pneumonitis and presents that centrilobular fibrosis and bridging fibrosis are the important hallmarks of chronic hypersensitivity pneumonitis, even with a usual interstitial pneumonia-like pattern.

Role of surgical lung biopsy in separating chronic hypersensitivity pneumonia from usual interstitial pneumonia/idiopathic pulmonary fibrosis: analysis of 31 biopsies from 15 patients

BACKGROUND

Lung biopsy has been proposed as a criterion for diagnosis of chronic hypersensitivity pneumonia (HP), especially in patients without proven antigen exposure. Histologic findings in some suspected HP patients overlap with usual interstitial pneumonia (UIP) and nonspecific interstitial pneumonia (NSIP). We reviewed our experience to determine the specificity of histologic findings in surgical lung biopsies from patients with clinical diagnoses of HP.

METHODS

Surgical lung biopsies from patients with chronic HP, idiopathic pulmonary fibrosis, and idiopathic NSIP were reviewed retrospectively without knowledge of the clinical diagnosis. Each specimen was assigned a histologic diagnosis, and selected histologic findings were tabulated. Clinical data were abstracted from medical records.

RESULTS

Fifteen patients with clinical diagnoses of chronic HP underwent biopsy of one to three lobes. Ten showed features diagnostic of HP in all specimens. Two had discordant findings that included HP in one specimen and UIP or nonspecific changes in others. Biopsies from two showed only UIP, and one showed NSIP. Diagnostic features were present in all samples from 9 of the 11 patients with more than one biopsy site (81.8%). Three patients died of disease, including both patients from whom biopsies showed only UIP.

CONCLUSIONS

Most patients with a clinical diagnosis of chronic HP have supportive histologic findings in surgical lung biopsies. A subset of HP patients has findings indistinguishable from UIP. Sampling from more than one lobe may be helpful in separating HP from idiopathic pulmonary fibrosis.

Chronic bird fancier's lung: histopathological and clinical correlation. An application of the 2002 ATS/ERS consensus classification of the idiopathic interstitial pneumonias

BACKGROUND

Chronic bird fancier's lung (BFL) has often been misdiagnosed as one of the idiopathic interstitial pneumonias (IIPs).

METHODS

To define the clinical and pathological characteristics of chronic BFL, 26 patients with chronic BFL from whom a surgical lung biopsy specimen was taken between October 1992 and June 2001 were evaluated. The histopathological characteristics of the surgical lung biopsy specimens were examined and correlations between the histopathology and clinical characteristics were analysed. The quality of chronic inflammatory and fibrotic changes was expressed according to the 2002 ATS/ERS consensus classification of IIPs.

RESULTS

Two patients were diagnosed as having bronchiolitis obliterans organising pneumonia (BOOP)-like lesions, five as having cellular non-specific interstitial pneumonia (NSIP)-like lesions, and eight as having fibrotic NSIP-like lesions. The other 11 patients were considered to have usual interstitial pneumonia (UIP)-like lesions because of the temporal heterogeneous appearances of the fibrotic changes. However, fibrosis in these patients had developed in centrilobular as well as perilobular areas, suggestive of hypersensitivity pneumonitis. Nineteen patients (73.1%) had multinucleated giant cells, often with cholesterol clefts, while only five patients (19.2%) had granulomas. Patients with BOOP-like or cellular NSIP-like lesions tended to have recurrent acute episodes, whereas patients with UIP-like lesions had an insidious onset. Patients with BOOP-like or cellular NSIP-like lesions had a more favourable outcome than those with fibrotic NSIP-like and UIP-like lesions.

CONCLUSIONS

The qualities of chronic inflammatory and fibrotic lesions vary significantly among patients with chronic BFL but correlate with clinical features and prognosis.

Hypersensitivity pneumonitis: a multifaceted deceiving disorder

Hypersensitivity pneumonitis (HP) represents a group of immunologically mediated lung disorders provoked by recurrent exposure to various environmental agents. HP is multifaceted and may mimic almost any interstitial lung disease, some infectious diseases,and even bronchiolar disorders. In the absence of a diagnostic gold standard,diagnosis of HP requires a combination of clinical, environmental, radiologic, physiologic,and pathologic findings that represent a diagnostic challenge for clinicians and-in the chronic form-even for experienced pathologists. Therapeutic approach includes avoiding further exposure and, depending on the clinical form, the administration of a course of prednisone. New anti-inflammatory, immunoregulatory, and antifibrotic drugs are urgently needed for this and other interstitial lung diseases.

Chronic hypersensitivity pneumonitis caused by Aspergillus complicated with pulmonary aspergilloma

A 57-year-old man consulted our hospital with a history of the gradual onset of dyspnea and a productive cough. Chest computed tomographic (CT) scans showed a nodular shadow in a cavity lesion, and reticulonodular, cystic, and ground-grass opacities in the bilateral lung fields with honeycombing. He was diagnosed as having pulmonary aspergilloma and idiopathic pulmonary fibrosis (IPF). As an outpatient, he suffered from dyspnea upon physical exertion with exacerbation of the high-resolution CT (HRCT) opacities. An inhalation provocation test for Aspergillosis fumigatus was positive and chronic hypersensitivity pneumonitis (CHP) caused by Aspergillus was finally diagnosed. Insidious CHP is sometimes misdiagnosed as IPF. The diagnosis of insidious CHP should be made on the basis of a detailed history, specific HRCT findings, and lymphocyte-dominant bronchoalveolar lavage fluid cell findings.

New aspects of hypersensitivity pneumonitis

PURPOSE OF REVIEW

Hypersensitivity pneumonitis (HP) represents a complex pulmonary disorder of varying intensity and clinical presentation, which is characterized by a diffuse Tc1 immune response of lung parenchyma and airways in patients previously sensitized to one of more than 300 etiologic agents that may favor the HP reaction. This review describes recent data that have clarified some of the events that govern the development of the hypersensitivity reaction following exposure to the causative agents involved in this disease.

RECENT FINDINGS

A number of recent data clearly demonstrate that several cytokines and chemokines, which are secreted at sites of disease activity, participate in the pulmonary inflammatory responses taking place in the lung of patients with HP.

SUMMARY

The past few years have seen outstanding advances in the understanding of immunologic and molecular events involved in the pathogenesis of HP. It is possible that these data could allow the discovery of therapeutic targets in individuals chronically exposed to HP antigens and evolving towards pulmonary fibrosis.