Features Of Hypersensitivity Pneumonitis Research Articles

Modern concepts of clinical variants and features of hypersensitivity pneumonitis in children

Hypersensitivity pneumonitis (HP) (J67) is the most common interstitial lung disease in children and adolescents. The disease is immunologically determined, it can be a disease when exposed to various factors that cause harmful effects on the environment. The most significant are thermophilic actinomycetes, antigens of animal and fungal origin. Currently, cases of “two cases of infection” have been identified, when a genetic predisposition has been identified in case of detection of cases of antigen results in the implementation of diseases. Immunological studies in GP are mainly focused on identifying specific IgG to the “guilty” antigen. High-resolution computed tomography is the most sensitive method of visualizing the GP, pathological changes are detected in more than 90% of patients. According to the characteristics of the clinical course and duration of the disease, acute (lasting less than 6 months) and chronic (more than 6 months) variants of the disease are distinguished. The formation of fibrosis of the lung tissue up to the honeycomb lung is observed in approximately 18% of cases. There are variants of HP: with fibrous and non-fibrous (inflammatory) phenotype. The basis of drug therapy so far is systemic and inhaled glucocorticosteroids, the use of which is pathogenetically substantiated and clinically effective. The prospects for therapy are also associated with the use of antifibrotic drugs: pirfenidone and nintedanib, which slow down the decline in lung function and improve patient survival. At the same time, the exclusion of contact with a causally significant allergen plays a key role. Our own observations concern 280 children with GP aged 8 months to 16 years, including 70 patients in the first year of life. Most patients had a hereditary allergic burden (in 74%) and a causal factor was traced. The prognosis, with rare exceptions, was favorable. The main reasons for poor outcomes in GP are continued contact with a causally significant allergen, late diagnosis of the disease, and inadequate therapy.

Study of nasal mucosa histopathological changes in patients with hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is an interstitial lung disease that develops after inhalation of a variety antigens in susceptible individuals. The nasal mucosa is constantly exposed to these antigens that can irritate the respiratory mucosa. So, the purpose of this study was to study nasal histopathological changes in order to identify any shared pathological changes between the upper airways and the well-known pathological features of HP. 40 HP patients diagnosed at the Chest Department, Kasr Alainy hospital following ATS/JRS/ALAT guidelines were included. Patients were subjected to thorough history, high-resolution computed tomography, spirometry, cough evaluation test (CET), sinonasal outcome test-22 (SNOT-22), sinonasal examination and nasal mucosal biopsy by an otolaryngologist under visualization by a rigid nasal endoscope. The mean age of the patients was 46.2 ± 13.5 (85% were females and 15% were males). 90% of patients presented with cough and the mean CET was 17.15 ± 5.59.77.5% of patients suffered from sinonasal symptoms and the mean SNOT-22 was 12.18 ± 3.8. There was a significant correlation between the burden of sinonasal symptoms represented by the SNOT-22 and the severity of the cough represented by CET (r 0.40, p 0.01). 87.5% of HP patients had chronic inflammation of the nasal mucosa with predominant lymphocytic infiltration in 72.5% of patients. 77.5% of HP patients had a high burden of sinonasal symptoms which is positively associated with cough severity. 72.5% of patients had predominately lymphocytic infiltration of the nasal mucosa.Trial registration: retrospectively registered, registration number is NCT05723796, date of registration 13/02/2023.

Hypersensitivity pneumonitis: Principles in diagnosis and management.

Hypersensitivity pneumonitis: Principles in diagnosis and management.

The Challenging Diagnosis of Interstitial Lung Disease in Children-One Case Report and Literature Review.

Childhood interstitial lung disease (chILD) includes a heterogeneous spectrum of rare respiratory disorders in children associated with substantial morbi-mortality. Interstitial tissue, and other pulmonary structures, epithelium, blood vessels, or pleura are involved, resulting in a restrictive lung disfunction. Respiratory symptoms set in progressively and are often subtle, making thorough clinical history and physical examination fundamental. The etiology often is obscure. The clinical presentation mimics pneumonia or asthma, leading to a diagnostic delay. Challenging diagnosis may require genetic tests, bronchoalveolar lavage, or lung biopsy. Alongside general supportive therapeutic measures, anti-inflammatory, immunosuppressive or antifibrotic agents may be used, based on data derived from adult studies. However, if accurate diagnosis and treatment are delayed, irreversible chronic respiratory failure may ensue, impacting prognosis. The most frequent chILD is hypersensitivity pneumonitis (HP), although it is rare in children. HP is associated with exposure to an environmental antigen, resulting in inflammation of the airways. Detailed antigen exposure history and identification of the inciting trigger are the cornerstones of diagnostic. This article provides the current state of chILD, revealing specific features of HP, based on a clinical case report of a patient admitted in our clinic, requiring extensive investigations for diagnosis, with a favorable long-term outcome.

Clinical Features of Hypersensitivity Pneumonitis in Children: A Single Center Study.

BackgroundHypersensitivity pneumonia (HP) is an interstitial lung disease (ILD) mainly involving small airways and lung parenchyma that is caused by the inhalation of antigens in susceptible people to stimulate the body's immune response.MethodsA total of 6 Chinese children with HP treated in our center from July 2017 to July 2021 were included in our study.ResultsAmong the children, there were 4 males and 2 females, ranging in age from 4 to 14 years. Three cases had chest tightness and shortness of breath, 2 cases had cough, 1 case had chest pain, and 1 case had fever. Two cases of children had a history of close contact with pet dogs, 1 case had a history of contact with pigeons, 2 cases lived in a moldy house recently, and 1 case recently played a saxophone that had been idle for more than 2 years. The parents of two cases also had similar symptoms recently. The specific signs of chest HRCT of 6 cases all were in line with the characteristics of HP. After avoiding the sensitization environment, 2 children quickly recovered, 4 patients received low-dose glucocorticoid oral treatment, and after symptom control the dose was gradually reduced. The course of treatment was about 3–6 months.ConclusionsExposure to a potential antigen has been found in all 6 HP children. The clinical manifestations are heterogeneous and easy to confuse with other diseases. A clear history of exposure to the antigens, respiratory symptoms associated with HP, signs of HP on HRCT, and improvement after removal from the antigenic environment constitute the cornerstone of the diagnosis of HP children in our unit. Avoiding exposure to antigenic environment is the first step in treatment, and glucocorticoid use is necessary in children with persistent symptoms.

Hypersensitivity pneumonitis: clinical, radiological and pathological profile of 103 patients from North India.

Hypersensitivity pneumonitis (HP) is an interstitial lung disease, commonly occurring due to exposure to various inciting agent related to occupation. Few studies have shown that it can also occur without any occupation exposure. In this study we are presenting clinical, radiological and bronchoscopic finding of 103 HP patients. We retrospective analysis of 5½ years HP patient's data from a chest institute of India. The diagnosis of HP was considered with following criteria: i) known exposure to an inciting antigen; ii) presence of respiratory symptoms; iii) radiologic evidence of diffuse lung disease; iv) no other identifiable cause; v) lung biopsy specimen that demonstrated features of HP; and vi) bronchoalveolar lavage lymphocytosis (≥30%). The mean ±SD age was 47±12.8 years; 67% were female. The common symptoms were cough (97%) and dyspnea (91%). History of exposure to inciting agent was present in 61% with pigeon exposure being the most common (56%). Majority of patients (86%) were having chronic symptoms for >6 months. On 6MWT oxygen desaturation >4% was seen in 57% patients. Centrilobular nodules (61%) and ground glass opacity (47.5%) were common finding on HRCT chest. Bronchoalveolar lavage (BAL) lymphocytosis >30% was present in 48.5% and histopathological diagnosis HP on transbronchial lung biopsy (TBLB) and/or endobronchial lung biopsy (EBLB) was in 50% patients. HP is exposure related environmental disease, as it can occur without any occupational history. Bronchoscopy with BAL and lung biopsy should do in all suspected cases to confirm diagnosis in our country as it is less invasive, day care procedure with less complication.

Non-necrotizing granulomatous pneumonitis and chronic pleuritis in soldiers deployed to Southwest Asia.

Reports of respiratory illnesses among soldiers returning from Southwest Asia have been described. During deployment to Southwest Asia, soldiers are exposed to various respiratory hazards, including dust storms, smoke from burn pits and industrial air pollutants. A few studies have reported increased rates of constrictive bronchiolitis and asthma in these patients. We sought to expand upon the pathological findings in this cohort. Lung biopsies from veterans of Southwest Asia were identified and re-reviewed. All patients had undergone pulmonary function tests and chest high-resolution CT imaging with no significant findings. Overall, 59patients with a history of inhalational exposure to at least one of the following were identified: smoke from burn pit, dust storm and sulphur plant fire. Samples included video-assisted thoracoscopic lung biopsies (57 of 59, 96.6%) and cryobiopsies (two of 59, 3.4%). Patients were predominantly male (54 of 59, 91.5%) with an age range of 24-55years (mean and median=35). Non-necrotising, poorly formed granulomas were identified in 22cases (22 of 59, 37.2%). The granulomas were mainly bronchiolocentric and were associated with chronic lymphoplasmacytic bronchiolitis, similar to hypersensitivity pneumonitis (HP). Pleural reaction in the form of focal chronic lymphocytic pleuritis and/or focal pleural adhesions were seen in 43 of 57 (75.4%) biopsies. To our knowledge, this is the first study to report pleural reaction as well as features of HP in this population, suggesting that pleural reaction and HP may be part of the spectrum of Southwest Asia deployment-related lung diseases.

A Mistaken Case of Sarcoid

SESSION TITLE: Fellow Case Report Poster - Diffuse Lung Disease II SESSION TYPE: Affiliate Case Report Poster PRESENTED ON: Tuesday, October 25, 2016 at 01:30 PM - 02:30 PM INTRODUCTION: Chronic hypersensitivity pneumonitis (HP) is a diffuse parenchymal lung disease caused by repeat exposure to a variety of antigens. It can mimic several interstitial lung diseases radiologically and pathologically making it difficult to differentiate. CASE PRESENTATION: A 40 year old female was referred to our pulmonary clinic for ILD evaluation after recently immigrating from Pakistan. She reported years of debilitating cough progressive dyspnea. She lived in an urban region and denied any significant organic or chemical exposures. Her initial pulmonary function testing (PFTs) suggested severe restrictive lung disease and her CT Chest revealed coarse upper lobe reticulation and architectural distortion. Despite non-revealing trans-bronchial and EBUS biopsies at the time, she was started on prednisone therapy for presumed sarcoidosis. Notably, her steroids were begun just months before her move and she reported persistent improvement in her symptoms since, despite the lack of objective changes in PFTs and CT chest on our assessment. Extensive serologic evaluation for an etiology revealed only antibodies to pigeon droppings which were not consistent with her history. She underwent VATs biopsy which revealed many poorly formed granulomas, severe diffuse interstitial fibrosis, cholesterol clefts, and Schumann bodies. Her final diagnosis was deemed to be chronic HP with fibrosing NSIP pattern. DISCUSSION: A definitive diagnosis for HP requires exposure to a known antigen and the assemblage of clinical, radiologic, laboratory, and pathologic findings. Due to the similar pathological features of NSIP and Chronic HP, the diagnosis remains a challenge. While acute HP may respond to immunosuppressive therapy, it is less clear whether patients with severe disease with an unclear precipitant would benefit from such therapy. In our case, it is unclear if the steroids or the environmental change (or both) may have halted the progression of her already severe disease. Thereby making the decision for long term immunosuppression a more difficult one. CONCLUSIONS: There remain large gaps in our knowledge with regards to the management of chronic HP, necessitating the need for larger case series or prospective trials. Reference #1: Churg A, Sin DD.Pathologic patterns and survival in chronic HP. Am J Sur Path.2009Dec;33(12)1765-70. Reference #2: Selman M, Pardo A. HP:insights in diagnosis and pathobiology. Am J Respir Crit Care Med 2012;186:314-324. Reference #3: Vourlekis JS, Schwarz MI.NSIP as the sole histologic expression of HP.Am J Med 2002;112:490-493. DISCLOSURE: The following authors have nothing to disclose: Mohammed Siddiqui, Omid Savari, Yasir Tarabichi No Product/Research Disclosure Information

The usefulness of KL-6 and SP-D for the diagnosis and management of chronic hypersensitivity pneumonitis

BackgroundIt is believed that Krebs von den Lungen-6 (KL-6) and surfactant protein D (SP-D) are useful biomarkers for the diagnosis of various types of interstitial lung diseases, including hypersensitivity pneumonitis (HP). The clinical features of chronic HP are similar to those of idiopathic interstitial pneumonias, especially idiopathic pulmonary fibrosis (IPF). ObjectiveWe sought to clarify the usefulness of serum KL-6 and SP-D for the diagnosis and management of chronic HP. MethodsWe examined serum KL-6 and SP-D levels and retrospectively evaluated the clinical parameters of acute HP (n = 35), chronic HP (n = 57), IPF (n = 54), collagen vascular disease-associated interstitial pneumonia (CVD-IP) (n = 67), and sarcoidosis (n = 47). We analyzed the relations between the two biomarkers and clinical data in chronic HP. ResultsSerum KL-6 and SP-D levels in acute HP (2710 U/ml and 338 ng/ml, median) and chronic HP (1500 U/ml and 264 ng/ml, median) were significantly higher than in IPF, CVD-IP, and sarcoidosis. The area under the curve (AUC) values for serum KL-6 and SP-D between chronic HP and IPF were 0.771 and 0.729, respectively. Serum KL-6 levels in chronic HP were significantly higher during episodes of acute exacerbation than 1 month before acute exacerbation. The serum KL-6 levels had correlations with serum SP-D and the percentage of lymphocytes in bronchoalveolar lavage fluid. ConclusionsSerum KL-6 and SP-D levels are useful for the diagnosis and management of chronic HP.

Validation of inhalation provocation test in chronic bird-related hypersensitivity pneumonitis and new prediction score.

Hypersensitivity pneumonitis (HP) is an immunologically mediated lung disease induced by the inhalation of any of a wide variety of antigens. For example, bird-related HP (BRHP) results from the inhalation of avian antigens. The clinical features of chronic HP, including imaging and histological findings, are similar to those of idiopathic pulmonary fibrosis. Despite its status as the "gold standard," the inhalation provocation test (IPT) is rarely performed, because the methods and the criteria are not standardized. In 2000, we reported the utility of IPT for pigeon dropping extracts. The purpose of the current study was to validate the utility and safety of the test, and to differentiate chronic HP from other interstitial lung diseases. A total of 28 patients with chronic BRHP and 19 control subjects were evaluated in this retrospective study. We validated the previous criteria and proposed new criteria using prediction scores. In the IPT using pigeon dropping extracts, the previous criteria showed a sensitivity of 78.6% and a specificity of 94.7% in this retrospective study. The increases in the peripheral white blood cell count and C-reactive protein levels are good indicators of a positive response to the inhalation challenge. We propose the use of the IPT prediction score (∆WBC [%] + 2 × ∆P[a - a]O2 [mm Hg], where WBC is white blood cell) and the prediction rule, which showed high sensitivity and specificity values of 92.9 and 94.7%, respectively. Two (1.5%) out of a total of 130 subjects who underwent the tests required treatment after the challenge. The IPT is a useful and safe tool for the diagnosis of chronic HP. The IPT prediction score that we have proposed has high sensitivity and specificity in the diagnosis of chronic BRHP.

Clinicopathological diagnosis of hypersensitivity pneumonitis

To enhance the understandings of clinical, radiological and pathological features of hypersensitivity pneumonitis (HP). Six HP cases with pathological data, clinical and radiological data were retrospectively analyzed during the period from February 2009 to September 2011 at Beijing Hospital of Ministry of Health. There were 2 males and 4 females with a mean age of 51.5 years (range: 38-61). Clinically, the patients presented with chronic cough, shortness of breath and dyspnea (n = 2). The disease course was 1-8 months. Five cases had fed pigeons and other contact histories. Specimens obtained by transbronchial lung biopsy (n = 3) and open lung biopsy (n = 3) were paraffin embedded and stained by hematoxylin and eosin, special stains and immunohistochemistry. Four cases had subacute HP and 2 cases chronic HP. Three cases of subacute HP underwent transbronchial lung biopsy. One case of subacute HP and 2 cases of chronic HP were diagnosed by open lung biopsy. High-resolution computed tomography of lungs showed diffuse ground glass and patch shadow along the bronchial and centrilobular distributions. There was a predominance of upper half zone. Typical visible mosaic syndrome was present. There was poorly formed granuloma without cheesy necrosis. With an insidious medical history and complicated radiological features, chronic HP cases were characterized by pulmonary interstitial fibrosis. There were usual interstitial pneumonitis (UIP)-like fibrosis and fibrosis with an airway-centered distribution type. The lesions were distributed around bronchioles. Continuous bridge fibrosis might be present. There were bronchiolar metaplasia of peribronchiolar alveoli, poorly formed granuloma and multinucleated giant cells in interstitium. Schaumann body was identified in 1 case. Because of its diverse clinical, radiological and pathological features, HP may be easily confused with other interstitial lung diseases. Aggregate analyses yield a definite diagnosis.

Multidetector row CT scan in hypersensitivity pneumonitis: Contribution of minimum intensity projection reformation

The objective of this pictorial essay is to highlight the key role of computed tomography scanning (CT scan), particularly minimum intensity projection (MinIP) reformation, with regards to the diagnosis of hypersensitivity pneumonitis (HP) and its contribution to patients' management. MinIP enhances detecting the characteristic CT scan features of HP, particularly air trapping and ground-glass opacities, features representing the bronchoalveolar lavage or biopsy core target zones to the clinician.

Alveolar proteinosis with hypersensitivity pneumonitis: A new clinical phenotype

The aim of the present study was to report the features of five patients with concurrent histopathological features of pulmonary alveolar proteinosis (PAP) and hypersensitivity pneumonitis (HP) and their high-resolution CT (HRCT) appearances. Patients with histopathological features of both HP and PAP on surgical lung biopsy referred for tertiary review were retrospectively identified. The pathology and HRCT images were semi-quantitatively scored to evaluate the relative contribution to HP and PAP. Five patients had histopathological features of HP and PAP but had varied HRCT appearances. All had imaging features of PAP to a varying degree with two patients also showing characteristics of HP but three patients had ill-defined thickened interlobular septa, not typical of either disease. We describe the coexistence of PAP and HP in five patients and discuss possible linkages between these two distinct pathologies.

Clinical Characteristics of Hypersensitivity Pneumonitis Proved by Lung Biopsy and Experiences With Clinical Diagnosis

PURPOSE: Hypersensitivity pneumonitis (HP) is highly variable and its diagnosis clinically challenging. To identify and analyze the clinical features of HP proved by lung biopsy and extend the experiences to guide the clinic diagnosis of the disease.

The possible involvement of immune complexes in pulmonary granuloma formation in experimental hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is a disease caused by inhaled organic dust. The alveolitis and granuloma are characteristic features of HP. The precise mechanism of granuloma formation is still unclear. The roles of immune complexes and primed T cell in relation to granuloma formation were studied. Local lymph node cells were obtained from C57BL/6 mice immunized by injection of ovalbumin (OA) or keyhole limpet haemocyanin (KLH) emulsified in complete Freund's adjuvant into footpads. Thereafter enriched T cells were obtained by passage through nylon wool columns. Antigens (OA, KLH) were chemically coupled to Sepharose 4B beads (OA-beads, KLH-beads). The immune complex was made by the incubation of the antigen-coupled beads and the immunized mouse serum at 37 degrees C for 2 hours. The recipient mouse irradiated by 6.5 Gy was transferred with 3 X 10(7) T cells and challenged with intratracheal instillation of 1 X 10(4) antigen-coupled beads or 1 X 10(4) immune complex-coupled beads. The recipient mice were sacrificed day 3 after cell transfer and challenge. The radius of pulmonary granuloma was measured by microscopic examination of the HE-stained section. The radius of granuloma increased in the recipient mouse which received the primed T cell and was challenged with immune complex-coupled beads compared with any other combination of cell transfer and antigen challenge. This result suggests that not only T cell but also immune complexes play an important role in granuloma formation in HP.

Hot Tub Associated Granulomatous Lung Disease From Mycobacterial Bioaerosols

Abstract: Exposure to microbial aerosols from indoor hot tubs and therapy pools can cause granulomatous lung disease. However, the clinical presentation, causative antigen, and factors affecting outcome remain poorly understood. We performed a retrospective case series of all patients seen at our institution from 1994 to 2002 with a diagnosis of hypersensitivity pneumonitis attributed to hot tub or therapy pool exposure (hot tub lung). We identified 27 immunocompetent patients with hot tub lung. The patients had symptoms accompanied by pulmonary function and high resolution chest computed tomography abnormalities suggestive for hypersensitivity pneumonitis. Nontuberculous mycobacteria (NTM) (mainly Mycobacterium avium complex) were cultured from most of the patients. Environmental sampling performed at a third of the implicated sites showed high concentrations of NTM in both air and water samples. Removal from exposure combined with oral corticosteroids and, in a few cases, NTM antibiotics, led to significant improvement or resolution of illness in all affected, although mild residual functional abnormalities persisted in the majority. Exposure to aerosols containing NTM from indoor warm water pools and spas can cause a granulomatous lung disease with features of hypersensitivity pneumonitis. Recognition of these environmental exposure sources and appropriate management leads to a generally favorable prognosis.

Chronic Hypersensitivity Pneumonitis: Differentiation from Idiopathic Pulmonary Fibrosis and Nonspecific Interstitial Pneumonia by Using Thin-Section CT

To retrospectively assess the accuracy of thin-section computed tomography (CT) in distinguishing chronic hypersensitivity pneumonitis (HP) from idiopathic pulmonary fibrosis (IPF) and nonspecific interstitial pneumonia (NSIP), with histologic results as the reference standard. This retrospective study was approved by the institutional research boards of the participating centers, and informed consent was waived. There was HIPAA compliance for all U.S. patients. The study included 66 patients (36 men, 30 women; mean age, 58.8 years +/- 10.9 [standard deviation]) with proved chronic HP (n = 18), IPF (n = 23), or NSIP (n = 25) who underwent CT. Two independent readers assessed the CT images, made a first-choice diagnosis, and noted the degree of confidence in the diagnosis. A general linear model was used to identify CT features that independently differentiated chronic HP from IPF and NSIP. Weighted kappa statistic was used to assess interobserver agreement. The CT features that best differentiated chronic HP were lobular areas with decreased attenuation and vascularity, centrilobular nodules, and absence of lower zone predominance of abnormalities (P < or = .008). The features that best differentiated NSIP were relative subpleural sparing, absence of lobular areas with decreased attenuation, and lack of honeycombing (P < or = .002). The features that best differentiated IPF were basal predominance of honeycombing, absence of relative subpleural sparing, and absence centrilobular nodules (P < or = .004). A confident diagnosis was made in 70 (53%) of 132 readings. This diagnosis was correct in 66 (94%) of 70 readings. The accuracy for the entire cohort was 80%. Interobserver agreement for confident diagnosis was good to excellent (kappa = 0.77-0.96). Characteristic CT features of chronic HP, IPF, and NSIP allow confident distinction between these entities in approximately 50% of patients.

Causes and Presenting Features in 85 Consecutive Patients With Hypersensitivity Pneumonitis

To assess the current spectrum of causes and clinical features associated with hypersensitivity pneumonitis (HP). We studied consecutive patients with HP diagnosed at the Mayo Clinic in Rochester, Minn, from January 1, 1997, through December 31, 2002. Diagnostic criteria for HP included the following: (1) presence of respiratory symptoms, (2) radiologic evidence of diffuse lung disease, (3) known exposure or a positive serologic test result to an inciting antigen, and (4) no other identifiable cause for the lung disease. If there was no identifiable inciting antigen, 1 of the following 2 criteria was required: (1) lung biopsy specimen that demonstrated features of HP or (2) bronchoalveolar lavage lymphocytosis and high-resolution computed tomographic evidence of ground-glass opacities or centrilobular nodules bilaterally. The mean +/- SD age of the 85 study patients was 53 +/- 14 years; 53 patients (62%) were women. Only 2 patients (2%) were current smokers. Chronic (> or = 4 months) respiratory symptoms were present in 66 patients (78%). Histopathologic confirmation was obtained in 64 patients (75%). The cause was identified in 64 patients (75%), and the most common causes were avian antigens (34%) and Mycobacterium avium complex in hot tub water (21%). Farmer's lung disease accounted for 11% of cases, and an additional 9% were related to household mold exposure. The inciting antigen was not identifiable in 25% of patients. Most patients with HP seen at this tertiary care referral center in the Midwest region of the United States had chronic HP, and the most common causes were exposure to birds and exposure to hot tubs.

Hypersensitivity Pneumonitis: Spectrum of High-Resolution CT and Pathologic Findings

The purpose of this article is to illustrate the spectrum of pathologic and high-resolution CT features of hypersensitivity pneumonitis (HP). High-resolution CT plays an important role in the diagnosis of HP. A confident diagnosis of subacute HP is based on the presence of ground-glass opacities, poorly defined centrilobular nodules, and mosaic attenuation on inspiratory images and of air trapping on expiratory CT images. Chronic HP is characterized on high-resolution CT by the presence of reticulation due to fibrosis superimposed on findings of subacute HP. Histologically, subacute HP is characterized by the presence of cellular bronchiolitis, noncaseating granulomas, and bronchiolocentric lymphocytic interstitial pneumonitis. Areas of organizing pneumonia also may be seen. The high-resolution CT and pathologic features of chronic HP frequently overlap with those of nonspecific interstitial pneumonia and usual interstitial pneumonia. Awareness of the various manifestations of HP is important for early diagnosis and management.

Surgical pathology of granulomatous interstitial pneumonia.

Agranulomatous interstitial pneumonia is a form of diffuse lung disease in which granulomas are a component of the histologic findings. The differential diagnosis is quite broad, but most cases represent examples of either sarcoidosis, diffuse granulomatous infections, or hypersensitivity pneumonitis. "Hot tub lung" is a recently described form of granulomatous interstitial pneumonia that appears to have some features of diffuse infections and some features of hypersensitivity pneumonitis. The pathologist's approach to these conditions can be facilitated by giving careful attention to the anatomic distribution of the granulomas, the qualitative features of the granulomas, and the histologic changes in the lung tissue around and away from the granulomas. These features, along with the results of cultures and special stains for micro-organisms and clinical and radiologic correlation allow for a diagnosis in the vast majority of cases.