Interstitial pneumonia with autoimmune features: a new classification still on the move

Interstitial Pneumonia with Autoimmune Features: What the Rheumatologist Needs to Know

PURPOSE OF REVIEW

This narrative review will focus on the role of the rheumatologist in evaluating patients with interstitial lung disease (ILD) without a defined rheumatic disease and will outline the current classification criteria for interstitial pneumonia with autoimmune features (IPAF) and describe what is known regarding IPAF pathobiology, natural history, prognosis, and treatment. Lastly, knowledge gaps and opportunities for future research will be discussed.

RECENT FINDINGS

IPAF is a recently defined classification of ILD patients who have features suggesting an autoimmune-mediated process, but do not fulfill current rheumatic disease criteria. The goal of the IPAF criteria is to provide a uniform case definition for the study of autoimmune ILD patients who do not currently fit within standard ILD diagnostic categories, ultimately improving diagnosis and therapy. Many of these patients are referred for rheumatologic evaluation to aid the diagnostic process. The care of the IPAF patient is complex and is multidisciplinary with pulmonology, rheumatology, pathology, radiology, physical therapy, primary care, pulmonary transplant providers all serving vital roles. The rheumatologist has several roles which include classification, disease monitoring, and management.

Interstitial Pneumonia with Autoimmune Features: Why Rheumatologist-Pulmonologist Collaboration Is Essential

In 2015 the European Respiratory Society (ERS) and the American Thoracic Society (ATS) “Task Force on Undifferentiated Forms of Connective Tissue Disease-associated Interstitial Lung Disease” proposed classification criteria for a new research category defined as “Interstitial Pneumonia with Autoimmune Features” (IPAF), to uniformly define patients with interstitial lung disease (ILD) and features of autoimmunity, without a definite connective tissue disease. These classification criteria were based on a variable combination of features obtained from three domains: a clinical domain consisting of extra-thoracic features, a serologic domain with specific autoantibodies, and a morphologic domain with imaging patterns, histopathological findings, or multicompartment involvement. Features suggesting a systemic vasculitis were excluded. Since publication of ERS/ATS IPAF research criteria, various retrospective studies have been published focusing on prevalence; clinical, morphological, and serological features; and prognosis of these patients showing a broad heterogeneity in the results. Recently, two prospective, cohort studies were performed, confirming the existence of some peculiarities for this clinical entity and the possible progression of IPAF to a defined connective tissue disease (CTD) in about 15% of cases. Moreover, a non-specific interstitial pneumonia pattern, an anti-nuclear antibody positivity, and a Raynaud phenomenon were the most common findings. In comparison with idiopathic pulmonary fibrosis (IPF), IPAF patients showed a better performance in pulmonary function tests and less necessity of oxygen delivery. However, at this stage of our knowledge, we believe that further prospective studies, possibly derived from multicenter cohorts and through randomized control trials, to further validate the proposed classification criteria are needed.

The Spectrum of Interstitial Lung Disease Associated with Autoimmune Diseases: Data of a 3.6-Year Prospective Study from a Referral Center of Interstitial Lung Disease and Lung Transplantation

Interstitial lung disease (ILD) may occur in patients with a rheumatic autoimmune disease (AD), increasing their risk of morbidity and mortality. However, little is known about the prevalence of AD in patients diagnosed with an ILD. In this prospective study, we determined the spectrum of ILD associated with AD (AD-ILD) among patients sent for assessment to a single clinic of ILD and lung transplantation from a referral center between May 2016 and December 2019. ILD diagnosis was made by pneumologists based on clinical and radiological findings and pulmonary function test abnormalities. All patients with ILD were also assessed by experienced rheumatologists. During the period of assessment, 338 patients were diagnosed with ILD. Among them, 32.8% fulfilled definitions for an AD. Most cases with AD-ILD had a diagnosis of rheumatoid arthritis (27.0%), systemic sclerosis (26.1%) or anti-synthetase syndrome (17.1%). Interestingly, 18% of the patients with AD-ILD were diagnosed as having an interstitial pneumonia with autoimmune features. Antinuclear antibodies and non-specific interstitial pneumonia were the most frequent positive autoantibodies and radiological pattern found in AD-ILD patients, respectively. In conclusion, our study indicates that a high number of ILD patients have a related AD. Consequently, close collaboration among rheumatologists and pneumologists is needed.

Interstitial Pneumonia with Autoimmune Features

Interstitial pneumonia with autoimmune features (IPAF) is a research classification proposed by the European Respiratory Society/American Thoracic Society Task Force on Undifferentiated Forms of Connective Tissue Disease-associated Interstitial Lung Disease as an initial step to uniformly define, identify, and study patients with interstitial lung disease (ILD) who have features of autoimmunity, yet fall short of a characterizable connective tissue disease. Since its publication in July 2015, there has been substantial interest in IPAF. Centers from around the world have published their findings of retrospectively identified cohorts of patients who fulfill IPAF criteria, suggestions for modification of the criteria have been offered, and patients who fulfill IPAF criteria are being included as a subset in the ongoing phase II multicenter unclassifiable ILD treatment trial with pirfenidone. The IPAF designation represents an important first step toward studying and furthering our understanding of the natural history of this cohort of patients with ILD using uniform nomenclature and a standardized set of criteria. Prospective evaluations and, ideally, interdisciplinary and multicenter collaborations will inform best practices for treatment and management and will guide future refinement to the IPAF criteria. This review focuses on the relevant background that led to the development of IPAF, summarizes the proposed criteria, discusses cohort studies of patients with IPAF published to date and what they have taught us about the IPAF phenotype, and offers insights into future directions in this arena. Clinical trial registered with www.clinicaltrials.gov (NCT03099187).

Clinical significance of thyroid hormone and antibodies in patients with idiopathic interstitial pneumonia

Background

Hypothyroidism was recently reported to be common and to predict mortality in patients with idiopathic pulmonary fibrosis (IPF). In addition, a high prevalence of hypothyroidism was shown in patients with idiopathic pleuroparenchymal fibroelastosis. However, in idiopathic interstitial pneumonia (IIP), a clinical significance of thyroid function has not been clarified in detail. The goal of this study was to investigate the clinical significance of thyroid function and the presence of thyroid antibodies in IIP.

Methods

We have reviewed IIP patients, and analyzed the positivity of thyroid antibodies at first. Next, the relationship of clinical characteristics with thyroid function and the positivity of thyroid antibodies was analyzed. Lastly, the positivity of thyroid antibodies and other autoantibodies was evaluated.

Results

In IIP patients, thyroglobulin and thyroid peroxidase antibodies were positive in 17 and 16%, respectively, and 22% of patients had either or both antibodies. Subclinical and/or overt hypothyroidism was confirmed in 7% of IIP patients. The free thyrotropin level had a significant positive correlation with vital capacity and a significant negative correlation with the C-reactive protein and surfactant protein-A levels, and erythrocyte sedimentation ratio (ESR). In addition, autoantibodies suggestive of connective tissue diseases (CTDs) were positive in more than two thirds of IIP patients with the thyroid antibody, and the positive rate of antinuclear and proteinase-3 anti-neutrophil cytoplasmic antibodies was significantly higher in IIP patients with thyroid antibodies than those without the antibodies.

Conclusions

Although thyroid dysfunction is not frequent, thyroid hormones and thyroid antibodies are possibly involved in the pathogenesis of IIP and their evaluation may be clinically useful to identify the clinical phenotype of IIP with autoimmune features.

Interstitial Pneumonia with Autoimmune Features

The European Respiratory Society/American Thoracic Society Task Force on Undifferentiated Forms of Connective Tissue Disease-associated Interstitial Lung Disease put forth the research classification interstitial pneumonia with autoimmune features as a step toward uniformly describing these patients. Diverse nomenclature and classification schemes had been proposed to characterize them. This classification has provided uniform nomenclature and criteria, fostering interdisciplinary engagement and research. Longitudinal surveillance is needed; some patients evolve to a defined connective tissue disease. This review discusses cohort studies of interstitial pneumonia with autoimmune features and what they have taught us about the phenotype, and offers insights into future directions.

Multidisciplinary Approach in the Early Detection of Undiagnosed Connective Tissue Diseases in Patients With Interstitial Lung Disease: A Retrospective Cohort Study

Interstitial lung disease (ILD) encompasses a wide range of parenchymal lung pathologies with different clinical, histological, radiological, and serological features. Follow-up, treatment, and prognosis are strongly influenced by the underlying pathogenesis. Considering that an ILD may complicate the course of any connective tissue disease (CTD) and that CTD's signs are not always easily identifiable, it could be useful to screen every ILD patient for a possible CTD. The recent definition of interstitial pneumonia with autoimmune features is a further confirmation of the close relationship between CTD and ILD. In this context, the multidisciplinary approach is assuming a growing and accepted role in the correct diagnosis and follow-up, to as early as possible define the best therapeutic strategy. However, despite clinical advantages, until now, the pathways of the multidisciplinary approach in ILD patients are largely heterogeneous across different centers and the best strategy to apply is still to be established and validated. Aims of this article are to describe the organization of our multidisciplinary group for ILD, which is mainly focused on the early identification and management of CTD in patients with ILD and to show our results in a 1 year period of observation. We found that 15% of patients referred for ILD had an underlying CTD, 33% had interstitial pneumonia with autoimmune feature, and 52% had ILD without detectable CTD. Furthermore, we demonstrated that the adoption of a standardized strategy consisting of a screening questionnaire, specific laboratory tests, and nailfold videocapillaroscopy in all incident ILD proved useful in making the right diagnosis.

Idiopathic and immune-related pulmonary fibrosis: diagnostic and therapeutic challenges

Interstitial lung disease (ILD) encompasses a large group of pulmonary conditions sharing common clinical, radiological and histopathological features as a consequence of fibrosis of the lung interstitium. The majority of ILDs are idiopathic in nature with possible genetic predisposition, but is also well recognised as a complication of connective tissue disease or with certain environmental, occupational or drug exposures. In recent years, a concerted international effort has been made to standardise the diagnostic criteria in ILD subtypes, formalise multidisciplinary pathways and standardise treatment recommendations. In this review, we discuss some of the current challenges around ILD diagnostics, the role of serological testing, especially, in light of the new classification of Interstitial Pneumonia with Autoimmune Features (IPAF) and discuss the evidence for therapies targeted at idiopathic and immune-related pulmonary fibrosis.

Interstitial pneumonia with autoimmune features show better survival and less exacerbations compared to idiopathic pulmonary fibrosis

BACKGROUND

Patients with interstitial lung disease (ILD) who show features related to autoimmunity without meeting criteria for a defined connective tissue disease are categorized as interstitial pneumonia with autoimmune features (IPAF). The present study compared clinical characteristics and clinical outcomes of patients with IPAF to patients with connective tissue disease related-interstitial lung disease (CTD-ILD) and patients with idiopathic pulmonary fibrosis (IPF).

METHODS

ILD patients who were consecutively enrolled in a single institution ILD cohort between 2008 and 2015 were evaluated for the study. Clinical data had been prospectively collected, while radiologic imaging and pathologic findings were re-reviewed for the present study.

RESULTS

Out of 305 patients with ILD, 54 (17.7%) patients met the classification of IPAF, 175 (57.4%) patients had IPF, and 76 (24.9%) patients were diagnosed with CTD-ILD. Compared to IPF, incidences of acute exacerbations in 1,3 and 5 years were significantly less in the IPAF group (p = 0.022, p = 0.026 and p = 0.007, respectively). From multivariate analysis for mortality, age (p = 0.034, HR 1.022, 95% CI: 1.002-1.044), FVC (p < 0.001, HR 0.970, 95% CI: 0.955-0.984), ILD exacerbation (p = 0.001, HR 2.074, 95% CI: 1.366-3.148), and ILD type (p = 0.047, HR 0.436, 95% CI: 0.192-0.984 (IPAF vs IPF), respectively) showed significant association.

CONCLUSIONS

Compared to the other ILD groups, IPAF showed distinct clinical characteristics. The IPAF group showed better survival and less episodes of exacerbation when compared to the IPF group.

Fibrosing interstitial lung diseases: knowns and unknowns

Patients with certain types of fibrosing interstitial lung disease (ILD) are at risk of developing a progressive phenotype characterised by self-sustaining fibrosis, decline in lung function, worsening quality of life, and early mortality. It has been proposed that such progressive fibrosing ILDs, which show commonalities in clinical behaviour and in the pathogenetic mechanisms that drive progressive fibrosis, may be "lumped" together for the purposes of clinical research and, potentially, for treatment. At present, no drugs are approved for the treatment of ILDs other than nintedanib and pirfenidone for the treatment of idiopathic pulmonary fibrosis. For other progressive fibrosing ILDs, the mainstay of drug therapy is immunosuppression. However, it is postulated that, once the response to lung injury in fibrosing ILDs has reached the stage at which fibrosis has become progressive and self-sustaining, targeted antifibrotic therapy would be required to slow disease progression. Nintedanib, an intracellular inhibitor of tyrosine kinases, has shown antifibrotic, anti-inflammatory and vascular remodelling effects in several non-clinical models of fibrosis, irrespective of the trigger for the injury. Ongoing clinical trials will provide insight into the role of antifibrotic treatment with nintedanib or pirfenidone in the management of fibrosing ILDs with a progressive phenotype.