Current Diagnosis and Management of Hypersensitivity Pneumonitis

Impact of Antigen Exposure on Outcomes and Treatment Response in Fibrotic Hypersensitivity Pneumonitis

BACKGROUND

Patients with fibrotic hypersensitivity pneumonitis (fHP) are frequently treated with immunosuppression to slow lung function decline; however, the impact of this treatment has not been studied across different types of antigen exposure.

RESEARCH QUESTION

In patients with fHP, do disease outcomes and response to treatment vary by antigen type?

STUDY DESIGN AND METHODS

A multicenter interstitial lung disease database (Canadian Registry for Pulmonary Fibrosis) was used to identify patients with fHP. The causative antigen was categorized as avian, mold, unknown, or other. Treatment was defined as mycophenolate ≥ 1,000 mg/d or azathioprine ≥ 75 mg/d for ≥ 30 days. Statistical analysis included t tests, χ2 tests, and one-way analysis of variance. Unadjusted and adjusted competing risks and Cox proportional hazards models were used to assess survival.

RESULTS

A total of 344 patients were identified with the following causative antigens: avian (n = 93; 27%), mold (n = 88; 26%), other (n = 15; 4%), and unknown (n = 148; 43%). Patient characteristics and lung function were similar among antigen groups with a mean FVC % predicted of 75 ± 20. The percent of patients treated with immunosuppression was similar between antigens with 58% of patients treated. There was no change in lung function or symptom scores with the initiation of immunosuppression in the full cohort. Immunosuppression was not associated with a change in survival for patients with avian or mold antigen (avian: hazard ratio, 0.41; 95% CI, 0.11-1.59; P = .20; mold: hazard ratio, 1.13; 95% CI, 0.26-4.97; P = .88). For patients with unknown causative antigen, survival was worse when treated with immunosuppression (hazard ratio, 2.65; 95% CI, 1.01-6.92; P = .047).

INTERPRETATION

Response to immunosuppression varies by antigen type in patients with fHP. Additional studies are needed to test the role of immunosuppression in fHP, and particularly in those with an unknown antigen.

A Case of Immunomodulator-Responsive Hypersensitivity Pneumonitis Secondary to Chronic Passive Smoke Inhalation

Hypersensitivity pneumonitis (HP) is a pulmonary disease characterized by inflammation and fibrosis of the lung parenchyma following chronic exposure to immunogenic antigens. The pathophysiology of HP involves type 3 and type 4 hypersensitivity reactions leading to acute and chronic manifestations, respectively. Clinically, it manifests as exertional dyspnea and wheezing. Pulmonary function tests display a pattern of restrictive lung disease, and high-resolution CT scans display a pattern of ground glass opacities, centrilobular nodules, and mosaic attenuation. Antigen avoidance remains the only method for primary prevention. Alternative therapy may be needed due to either the inability to avoid antigens or the lack of antigen identification. Prednisone 0.5 mg/kg per day is the first-line treatment for acute non-fibrotic forms of HP. In chronic or fibrotic HP, the immunomodulator mycophenolate mofetil (MMF) was shown to be an effective treatment in improving the diffusing capacity of the lungs for carbon monoxide and forced vital capacity, but not overall survival. The following study aims to bring to attention the need for additional prospective multicenter clinical trials to clarify the role of MMF as an immunomodulator in fibrosing HP.

Mechanisms and management of cough in interstitial lung disease

INTRODUCTION

Many patients with interstitial lung diseases (ILDs), especially fibrotic ILDs, experience chronic cough. It negatively impacts both physical and psychological well-being. Effective treatment options are limited.

AREAS COVERED

The pathophysiology of chronic cough in IPF is complex and involves multiple mechanisms, including mechanical distortion of airways, parenchyma, and nerve fibers. The pathophysiology of cough in other fibrosing ILDs is poorly understood and involves various pathways. The purpose of this review is to highlight mechanisms of chronic cough and to present therapeutic evidence for its management in the most commonly occurring diffuse fibrosing lung diseases including idiopathic pulmonary fibrosis (IPF), connective tissue disease-related interstitial lung disease (CTD-ILD), sarcoidosis-related ILD (Sc-ILD), chronic hypersensitivity pneumonitis-related ILD (CHP-ILD), and post-COVID-19-related interstitial lung disease (PC-ILD).

EXPERT OPINION

This review guides the management of chronic cough in fibrosing ILDs. In this era of precision medicine, chronic cough management should be individualized in each interstitial lung disease.

Acute Recreational Cannabis-Induced Hypersensitivity Pneumonitis: A Case Report

Hypersensitivity pneumonitis (HP) is a lung disease in which foreign matter is inhaled and exposed to lung parenchymal and interstitial tissue. Such matter may include pollen, molds, chemicals, and smoke. HP leads to widespread inflammation and even fibrosis in chronic forms; the main route of treatment usually involves corticosteroids and antifibrotics as needed. We describe a patient case in which HP was diagnosed after using recreational marijuana, and her chest x-ray had a complete resolution after one day of a corticosteroid regimen. As recreational marijuana use increases, clinicians need to keep HP on the differential diagnosis in patients that frequently utilize recreational marijuana obtained through illicit business.

Occupational hypersensitivity pneumonia

Hypersensitivity pneumonitis (HP) is an immunological lung disease that affects individuals who are sensitive and susceptible to occupational and environmental exposures. While clinical and radiological findings may resemble other interstitial lung diseases, identifying the causative agents can aid in the differential diagnosis. However, this can be challenging and may result in delayed diagnosis and poor prognosis. A gold standard test for diagnosis is currently unavailable, and therefore, a multidisciplinary approach involving a clinician, radiologist, and pathologist is necessary. Avoiding exposure is the first step in treatment, with immunosuppressive therapeutics also being used. Antifibrotic agents show promise for future treatment approaches. Despite recent advancements in data and guidelines, knowledge about managing occupational HP remains limited. This review provides a summary of the epidemiological, clinical, and radiological findings, as well as diagnostic and treatment principles of occupational HP based on current literature.

Dyskeratosis congenita with heterozygous RTEL1 mutations presenting with fibrotic hypersensitivity pneumonitis

Dyskeratosis congenita is a rare genetic disorder of telomere insufficiency characterized by a mucocutaneous triad of nail dystrophy, abnormal skin pigmentation, and mucosal leukoplakia. Early diagnosis is important for multidisciplinary approach to its complications including bone marrow failure, malignancy, interstitial lung disease, and liver disease which cause significant morbidity and mortality. We report a genetically confirmed case of dyskeratosis congenita who presented with fibrotic hypersensitivity pneumonitis, highlighting non-mucocutaneous features of dyskeratosis congenita and the need to consider genetic predisposition in a patient with interstitial lung disease and combined unusual manifestations.

Clinical characteristics and outcomes of hypersensitivity pneumonitis in South Korea

BACKGROUND

Hypersensitivity pneumonitis (HP) is an interstitial lung disease (ILD) that results from an immune-mediated reaction involving various antigens in susceptible individuals. However, the clinical characteristics and outcomes of HP in South Korea are not well understood.

OBJECTIVES

This study was conducted to identify the clinical characteristics and outcomes of HP in South Korea.

DESIGN

This is a retrospective observational study investigating patients with pathologically confirmed HP at our center, along with a comprehensive review of published HP cases in the Republic of Korea.

METHODS

This retrospective study analyzed 43 patients with pathologically proven HP at a single tertiary hospital in Korea between 1996 and 2020. In addition, case reports of HP published in Korea were collected. The clinical characteristics, etiologies, treatment, and outcomes of patients from our center, as well as case reports, were reviewed. Patients from our hospital were divided into fibrotic and nonfibrotic subtypes according to the ATS/JRS/ALAT guidelines.

RESULTS

Among 43 patients with biopsy-proven HP, 12 (27.9%) and 31 (72.1%) patients were classified into the fibrotic and nonfibrotic subtypes, respectively. The fibrotic HP group was older (64.6 ± 8.5 versus 55.2 ± 8.3, p = 0.002) with less frequent complaints of fever (0% versus 45.2%, p = 0.013) compared to the nonfibrotic HP group. The most common inciting antigen was household mold (21, 48.8%), followed by inorganic substances (6, 14.0%). Inciting antigens were not identified in eight (18.6%) patients. Treatment of corticosteroids was initiated in 34 (79.1%) patients. An analysis of 46 patients from Korea by literature review demonstrated that reported cases were relatively younger and drugs were the most common etiology compared to our cohort.

CONCLUSION

The analysis of reported cases, as well as our cohort, showed that exposure history and clinical manifestations are heterogeneous for patients with HP in South Korea.

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

Hypersensitivity pneumonitis (HP) is a complicated and heterogeneous interstitial lung disease (ILD) caused by an excessive immune response to an inhaled antigen in susceptible individuals. Accurate diagnosis of HP is difficult and necessitates a detailed exposure history, as well as a multidisciplinary discussion of clinical, histopathologic, and radiologic data. We provide a pictorial review based on the latest American Thoracic Society (ATS)/Japanese Respiratory Society (JRS)/Asociación Latinoamericana del Tórax (ALAT) guidelines for diagnosing HP through demonstrating new radiologic terms, features, and a new classification of HP which will benefit radiologists and pulmonologists.

Hypersensitivity pneumonia associated with metallic straw of mate (chimarrão): A case report

This case report describes a 61-year-old male who sought treatment for sudden symptoms of dry cough, chest pain and severe dyspnea. On admission, the patient had hypoxemia and predominantly medullary infiltrate that we could observe on his imaging exams. After hospital discharge, he presented two similar episodes, with clinical and radiological improvement with oxygen therapy alone. He denied exposure to birds, mold or chemical agents. However, the patient noticed the onset of symptoms soon after drinking chimarrão. Given the compatible clinical, radiological and laboratory history, the diagnosis of hypersensitivity pneumonitis was performed. The patient was instructed by the medical team not to consume the drink anymore, remaining asymptomatic for more than two years.

Longstanding hypersensitivity pneumonitis and its response to roflumilast: A review of its likely immunological effects

We describe the case of a 42yr old man with evidence of hypersensitivity pneumonitis referred with cough and breathlessness for several years which had further deteriorated in the prior 12 months. He had known atopic asthma without evidence of activation.

A chest CT scan showed widespread ground glass change in his lung fields. He had feather bedding at home and in his youth cleaned aviaries. His forced vital capacity and lung volumes were reduced along with oxygen saturations at rest (92% on air), overnight (83% on air) and upon walking (78%). Steroids were commenced for a total of 6 months with little consistent improvement in symptoms or objective measures and with no change in his CT scan appearance. As a result, a trial of roflumilast (a phosphodiesterase-4 inhibitor) was commenced due to its range of immunological effects and in order to avoid long-term immune suppression with mycophenolate motefil in a young patient.

On roflumilast treatment his cough and breathlessness improved at 4 weeks and the chest crackles cleared. An interval Chest CT scan showed resolution of the ground glass change with improved CT scores that are maintained 2 yrs. All oxygen measures improved and nocturnal oxygen was discontinued. His Lung function has remained largely stable on roflumilast and symptoms of cough and breathlessness have resolved. This case report reviews the immunology of hypersensitivity pneumonitis and the likely actions of Roflumilast relevant to this condition. It is the first published case report documenting its use in hypersensitivity pneumonitis.

[New developments in the management of hypersensitivity pneumonitis]

INTRODUCTION

Hypersensitivity pneumonitis (HP) is one of the most common interstitial lung diseases, characterized by an inflammatory and/or fibrotic reaction to inhaled antigens.

BACKGROUND

The heterogeneity of presentation and the lack of international guidelines makes management complex. In addition, the current treatment, based on antigen eviction and immunosuppressive drugs, is less effective in the fibrotic forms of HP. This article summarizes the latest data on HP and the new recommendations of the American Thoracic Society (ATS) on the diagnosis of HP.

CONCLUSION

The new ATS recommendations establish a more precise and rigorous diagnostic approach to HP. Multidisciplinary discussion plays a pivotal role both in the diagnosis and the treatment of the disease. Nintedanib has recently been shown to be effective in fibrotic HP.

PERSPECTIVES

Questions remain unanswered about the optimal therapeutic strategy in fibrotic HP, which underlines the need to carry out large-scale studies.

[Hypersensitivity Pneumonitis: An update]

Hypersensitivity Pneumonitis (HP) is a common immune-mediated interstitial lung disease (ILD) induced by repeated exposure to environmental antigens in susceptible individuals. The most commonly known forms are bird fancier's disease and farmer's lung. However, the antigens involved are widely diverse. Therefore, the list of causes of HP is frequently expanding. HP seems to be under-diagnosed owing to its highly heterogeneous presentation in both the non-fibrotic and fibrotic subtypes and could represent up to 15% of all ILDs encountered in clinical practice. However, the recognition of HP cases is essential to ensure appropriate therapy for the patient. Home health care workers' intervention is sometimes critical in this context. In case of confirmed exposure, the diagnosis could be considered with high confidence if the high-resolution computed tomography (HR-CT) shows a typical HP pattern associated with a lymphocytosis over 30% in the broncho-alveolar lavage (BAL). In all other situations, the patients should undergo further investigations and additional histopathological sampling should be considered and submitted to a multidisciplinary team discussion. After diagnosis, antigenic eviction is the rule whenever possible. Corticosteroid treatment is the first-line medical treatment for severe forms and aims to prevent the development of fibrosis. Anti-fibrotic therapy is now an option for patients with progressive ILD and failure of immunomodulatory/immunosuppressive therapies.

Sooty bark disease of maples: the risk for hypersensitivity pneumonitis by fungal spores not only for woodman

In the middle of the twentieth century, the from North America sooty bark disease (SBD) of maples was first discovered in England and has spread in the last decades in Central Europe, in particular. The trigger of SBD is the mould fungus Cryptostroma (C.) corticale. The most common infested maple is the sycamore, Acer pseudoplatanus, a common tree in woods and parks. The disease is characterised by peeling of the outer layer of the bark and brownish-black spores under the peeled off bark. These spores can cause maple bark disease (MBD) in humans, a hypersensitivity pneumonitis (HP) with similar symptoms like COPD, allergic asthma, influenza or flu-like infections and interstitial pneumonia. Persons who have intensive respectively occupational contact with infested trees or wood, e.g., woodman, foresters, sawyers or paper mill workers, are at risk in particular. Since C. corticale favours hot summers and host trees weakened by drought, SBD will increasingly spread in the future due to ongoing climate change. Consequently, the risk of developing MBD will increase, too. As with all HPs, e.g., farmer's lung and pigeon breeder's disease, the diagnosis of MBD is intricate because it has no clear distinguishing characteristics compared to other interstitial lung diseases. Therefore, the establishment of consistent diagnosis guidelines is required. For correct diagnosis and successful therapy, multidisciplinary expertise including pulmonologists, radiologists, pathologists and occupational physicians is recommended. If MBD is diagnosed in time, the removal of the triggering fungus or the infested maple wood leads to complete recovery in most cases. Chronic HP can lead to lung fibrosis and a total loss of lung function culminating in death. HP and, thus, MBD, is a disease with a very high occupational amount. To avoid contact with spores of C. corticale, persons working on infested wood or trees have to wear personal protective equipment. To protect the public, areas with infested maples have to be cordoned off, and the trees should be removed. This is also for impeding further spreading of the spores.

Rare imaging findings of hypersensitivity pneumonitis: A case report

BACKGROUND

Hypersensitivity pneumonitis (HP) is an immune-mediated syndrome caused by allergen inhalation. High-resolution computed tomography (HRCT) of HP may show diffuse ground-glass opacity, centrilobular ground-glass nodules, areas of air-trapping, thin-walled cysts, or fibrotic changes.

CASE SUMMARY

A 47-year-old male patient went to the hospital complaining of cough and gradual aggravation of shortness of breath. HRCT of the lung showed that multiple nodules and ground-glass high-density shadows were present in both lungs. In addition, circular high-density shadows of various sizes were widely distributed in both lungs with relatively normal lung markings inside them. But other tests did not have a positive finding that can clarify the cause. Therefore, the patient underwent a lung biopsy. The pathological results showed that the lesions tended to be HP. After 4 mo of follow-up, the lesions in the patient's lungs were absorbed spontaneously, and the symptoms of cough and shortness of breath have disappeared. The review results suggested that the patient’s disease was self-healing, which was consistent with the characteristics of HP.

CONCLUSION

For some patients with HP, abnormal HRCT findings, such as the lesions in the lungs, can be absorbed on their own, which is an important clue in the diagnosis of the disease. Early diagnosis by lung biopsy is necessary when antigen exposure is unknown.