Interstitial pneumonia with autoimmune features: challenges and controversies

Evaluation of Autoimmune Features in Patients with Idiopathic Pulmonary Fibrosis and Pathologic Usual Interstitial Pneumonia: Implications for CT Patterns and Prognosis

Background The clinical, radiologic, and prognostic implications of interstitial pneumonia with autoimmune features (IPAF) in patients with idiopathic interstitial pneumonia and pathologic usual interstitial pneumonia (UIP) have not been fully evaluated. Purpose To compare autoimmune features according to CT patterns for the diagnosis of idiopathic pulmonary fibrosis (IPF) and to assess the diagnostic and prognostic implications of IPAF in patients with IPF-UIP. Materials and Methods This retrospective study included patients with UIP confirmed by surgical lung biopsy between January 2013 and February 2020. Data regarding clinical, radiologic, and pathologic autoimmune features were collected, and patients were diagnosed with IPAF according to current guidelines. CT signs for connective tissue disease (CTD; anterior upper lobe, straightedge, and exuberant honeycombing signs) were also evaluated. Overall survival (OS) was evaluated using Cox proportional hazards models. Results Among 210 patients included (median age, 64 years; IQR, 60-68 years; 158 male patients), 23 (11.0%) had IPAF. Patients with an alternative diagnosis or CT pattern indeterminate for UIP showed a higher prevalence of autoimmune features that were pathologic (38% [33 of 87] vs 20.3% [25 of 123]; P = .005) and serologic (20% [17 of 87] vs 9.8% [12 of 123]; P = .04) and IPAF (4.1% [five of 123] vs 21% [18 of 87]; P < .001) compared with patients with UIP or probable UIP pattern. However, IPAF was not predictive of OS (hazard ratio [HR], 0.81; 95% CI: 0.38, 1.72; P = .58). Lymphoid follicles (HR, 0.59; 95% CI: 0.37, 0.93; P = .02), CT signs for CTD (HR, 0.31; 95% CI: 0.09, 0.99; P = .047), and use of an antifibrotic agent (HR, 0.31; 95% CI: 0.19, 0.51; P < .001) were independently associated with higher OS, and greater extent of fibrosis on CT scans was associated with worse OS (HR, 1.08; 95% CI: 1.05, 1.11; P < .001). Conclusion In patients with IPF-pathologic UIP, serologic and pathologic autoimmune features were associated with indeterminate or alternative CT patterns. Certain histopathologic and radiologic autoimmune features, but not current IPAF criteria, were associated with survival. © RSNA, 2025 Supplemental material is available for this article. See also the editorial by Ackman in this issue.

Proteomic profiling of bronchoalveolar lavage fluid uncovers protein clusters linked to survival in idiopathic forms of interstitial lung disease

Background

Idiopathic interstitial pneumonias (IIPs), such as idiopathic pulmonary fibrosis and interstitial pneumonia with autoimmune features, present diagnostic and therapeutic challenges due to their heterogeneous nature. This study aimed to identify intrinsic molecular signatures within the lung microenvironment of these IIPs through proteomic analysis of bronchoalveolar lavage fluid (BALF).

Methods

Patients with IIP (n=23) underwent comprehensive clinical evaluation including pre-treatment bronchoscopy and were compared with controls without lung disease (n=5). Proteomic profiling of BALF was conducted using label-free quantitative methods. Unsupervised cluster analyses identified protein expression profiles that were then analysed to predict survival outcomes and investigate associated pathways.

Results

Proteomic profiling successfully differentiated IIP from controls. k-means clustering based on protein expression revealed three distinct IIP clusters, which were not associated with age, smoking history, or baseline pulmonary function. These clusters had unique survival trajectories and provided more accurate survival predictions than the Gender Age Physiology index (concordance index 0.794 versus 0.709). The cluster with the worst prognosis featured decreased inflammatory signalling and complement activation, with pathway analysis highlighting altered immune response pathways related to immunoglobulin production and B-cell-mediated immunity.

Conclusions

The unsupervised clustering of BALF proteomics provided a novel stratification of IIP patients, with potential implications for prognostic and therapeutic targeting. The identified molecular phenotypes underscore the diversity within the IIP classification and the potential importance of personalised treatments for these conditions. Future validation in larger, multi-ethnic cohorts is essential to confirm these findings and to explore their utility in clinical decision-making for patients with IIP.

Interstitial pneumonia development after chemotherapy in B-cell non-hodgkin's lymphoma patients: clinical profiles and risk factors

Interstitial pneumonia (IP) is a significant adverse effect of chemotherapy in B-cell non-Hodgkin's lymphoma (NHL) patients. This study aimed to identify the clinical characteristics, risk factors, and treatment outcomes associated with IP in these patients. A retrospective review of 615 NHL patients treated at the Fourth Hospital of Hebei Medical University from 2016 to 2021 identified 50 patients with IP post-chemotherapy as the case group. A propensity score matched control group of 55 patients without pneumonia was established. Clinical profiles, risk factors, and treatment outcomes were evaluated. The IP incidence was 8.13% (50/615) in B-cell NHL patients. Multivariate analysis revealed liposomes, elevated lactate dehydrogenase (LDH), and erythrocyte sedimentation rate (ESR) as independent risk factors for IP. Receiver Operating Characteristic (ROC) curve analyses suggested that alterations in LDH and ESR could predict IP risk. The conclusion suggests that IP is associated with liposomal doxorubicin-induced lung injury and other cytotoxic chemotherapy, possibly due to Rituximab (RTX)-induced immune imbalance. Given the potential of IP with pulmonary infections, high-risk patients may need prophylactic antibiotics and appropriate corticosteroid therapy.

Machine Learning of Plasma Proteomics Classifies Diagnosis of Interstitial Lung Disease

Rationale: Distinguishing connective tissue disease-associated interstitial lung disease (CTD-ILD) from idiopathic pulmonary fibrosis (IPF) can be clinically challenging. Objectives: To identify proteins that separate and classify patients with CTD-ILD and those with IPF. Methods: Four registries with 1,247 patients with IPF and 352 patients with CTD-ILD were included in analyses. Plasma samples were subjected to high-throughput proteomics assays. Protein features were prioritized using recursive feature elimination to construct a proteomic classifier. Multiple machine learning models, including support vector machine, LASSO (least absolute shrinkage and selection operator) regression, random forest, and imbalanced Random Forest, were trained and tested in independent cohorts. The validated models were used to classify each case iteratively in external datasets. Measurements and Main Results: A classifier with 37 proteins (proteomic classifier 37 [PC37]) was enriched in the biological process of bronchiole development and smooth muscle proliferation and immune responses. Four machine learning models used PC37 with sex and age score to generate continuous classification values. Receiver operating characteristic curve analyses of these scores demonstrated consistent areas under the curve of 0.85-0.90 in the test cohort and 0.94-0.96 in the single-sample dataset. Binary classification demonstrated 78.6-80.4% sensitivity and 76-84.4% specificity in the test cohort and 93.5-96.1% sensitivity and 69.5-77.6% specificity in the single-sample classification dataset. Composite analysis of all machine learning models confirmed 78.2% (194 of 248) accuracy in the test cohort and 82.9% (208 of 251) in the single-sample classification dataset. Conclusions: Multiple machine learning models trained with large cohort proteomic datasets consistently distinguished CTD-ILD from IPF. Many of the identified proteins are involved in immune pathways. We further developed a novel approach for single-sample classification, which could facilitate honing the differential diagnosis of ILD in challenging cases and improve clinical decision making.

The autoimmune landscape of Porto-sinusoidal vascular disorder: What the rheumatologist needs to know

Porto-sinusoidal vascular disorder (PSVD) encompasses a group of vascular disorders characterized by lesions of the portal venules and sinusoids with clinical manifestations ranging from non-specific abnormalities in serum liver enzymes to clinically overt portal hypertension and related complications. Several reports have documented cases of PSVD in patients with systemic autoimmune conditions, such as systemic lupus erythematosus, systemic sclerosis, and rheumatoid arthritis. It is of note that these diseases share specific pathophysiological features with PSVD, including endothelial dysfunction, vascular inflammation, and molecular signatures. This narrative review aims to summarize the current knowledge on the association between PSVD and systemic autoimmune diseases, emphasizing the importance of promptly recognizing this condition in the rheumatological practice, and highlighting the key aspects where further research is necessary from both pathogenic and clinical perspectives.

Proteomic profiling of bronchoalveolar lavage fluid uncovers protein clusters linked to survival in idiopathic forms of interstitial lung disease

Background

Idiopathic interstitial pneumonias (IIPs) such as idiopathic pulmonary fibrosis (IPF) and interstitial pneumonia with autoimmune features (IPAF), present diagnostic and therapeutic challenges due to their heterogeneous nature. This study aimed to identify intrinsic molecular signatures within the lung microenvironment of these IIPs through proteomic analysis of bronchoalveolar lavage fluid (BALF).

Methods

Patients with IIP (n=23) underwent comprehensive clinical evaluation including pre-treatment bronchoscopy and were compared to controls without lung disease (n=5). Proteomic profiling of BALF was conducted using label-free quantitative methods. Unsupervised cluster analyses identified protein expression profiles which were then analyzed to predict survival outcomes and investigate associated pathways.

Results

Proteomic profiling successfully differentiated IIP from controls. k-means clustering, based on protein expression revealed three distinct IIP clusters, which were not associated with age, smoking history, or baseline pulmonary function. These clusters had unique survival trajectories and provided more accurate survival predictions than the Gender Age Physiology (GAP) index (C-index 0.794 vs. 0.709). The cluster with the worst prognosis featured decreased inflammatory signaling and complement activation, with pathway analysis highlighting altered immune response pathways related to immunoglobulin production and B cell-mediated immunity.

Conclusions

The unsupervised clustering of BALF proteomics provided a novel stratification of IIP patients, with potential implications for prognostic and therapeutic targeting. The identified molecular phenotypes underscore the diversity within the IIP classification and the potential importance of personalized treatments for these conditions. Future validation in larger, multi-ethnic cohorts is essential to confirm these findings and to explore their utility in clinical decision-making for patients with IIP.

Performance of GAP and ILD-GAP models in predicting lung transplant or death in interstitial pneumonia with autoimmune features

OBJECTIVES

To assess the ability of two risk prediction models in interstitial lung disease (ILD) to predict death or lung transplantation in a cohort of patients with interstitial pneumonia with autoimmune features (IPAF).

METHODS

We performed a retrospective cohort study of adults with IPAF at an academic medical centre. The primary outcome was a composite of lung transplantation or death. We applied the patient data to the previously described Gender-Age-Physiology (GAP) and ILD-GAP models to determine the ability of these models to predict the composite outcome. Model discrimination was assessed using the c-index, and model calibration was determined by comparing the incidence ratios of observed vs expected deaths.

RESULTS

Ninety-four patients with IPAF were included. Mean (s.d.) age was 58 (13.5) years and the majority were female (62%). The majority met serologic and morphologic criteria for IPAF (94% and 91%, respectively). The GAP model had a c-index of 0.664 (95% CI 0.547-0.781), while the ILD-GAP model had a c-index of 0.569 (95% CI 0.440-0.697). In those with GAP stage 1 or GAP stage 2 disease, calibration of the GAP model was satisfactory at 2 and 3 years for the cumulative end point of lung transplantation or death.

CONCLUSION

In patients with IPAF, the GAP model performed well as a predictor of lung transplantation or death at 2 years and 3 years from ILD diagnosis in patients with GAP stage 1 and GAP stage 2 disease.

Interstitial Pneumonia with Autoimmune Features: Aiming to Define, Refine, and Treat

Interstitial pneumonia with autoimmune features (IPAF) was defined for research purposes as interstitial lung disease (ILD) associated with features of autoimmunity without diagnosed rheumatic disease. Since publication of the IPAF criteria in 2015, there have been multiple studies of IPAF. However, much remains unknown regarding pathogenesis, prognosis, and treatment in IPAF. This narrative review details the history and classification of IPAF, lists challenges associated with classifying patients as IPAF, and explores the prevalence, epidemiology and presentation of IPAF. We also examine prognosis and important features determining IPAF clinical course, outline pathogenesis, and review treatment strategies.

Connective tissue disease-associated interstitial lung disease

Connective tissue disease-associated interstitial lung disease (CTD-ILD) represents a group of systemic autoimmune disorders characterized by immune-mediated organ dysfunction. Systemic sclerosis, rheumatoid arthritis, idiopathic inflammatory myositis, and Sjögren's syndrome are the most common CTDs that present with pulmonary involvement, as well as with interstitial pneumonia with autoimmune features. The frequency of CTD-ILD varies according to the type of CTD, but the overall incidence is 15%, causing an important impact on morbidity and mortality. The decision of which CTD patient should be investigated for ILD is unclear for many CTDs. Besides that, the clinical spectrum can range from asymptomatic findings on imaging to respiratory failure and death. A significant proportion of patients will present with a more severe and progressive disease, and, for those, immunosuppression with corticosteroids and cytotoxic medications are the mainstay of pharmacological treatment. In this review, we summarized the approach to diagnosis and treatment of CTD-ILD, highlighting recent advances in therapeutics for the various forms of CTD.

Unclassifiable interstitial lung disease and autoimmunity: Towards IPAF in children?

INTRODUCTION

Interstitial pneumonia with autoimmune features (IPAF) has been defined for adults with interstitial lung disease (ILD) and autoimmunity who do not meet the criteria for a specific connective tissue disease (CTD). We aimed to determine whether IPAF criteria could apply to children.

METHODS

We retrospectively studied patients with ILD and autoimmunity followed at Necker Hospital between 2008 and 2019. Children were classified according to specific CTD and IPAF criteria. The epidemiology and course of the disease were studied according to the final diagnosis.

RESULTS

Among 27 patients, 6 fulfilled the criteria for IPAF and represented 4.5% of all patients with ILD during the study period. Other diagnoses included juvenile dermatomyositis (30%), overlap syndromes (19%), systemic lupus erythematosus (15%), systemic sclerosis (7%), mixed CTD (4%), and rheumatoid arthritis (4%). IPAF patients were more frequently boys versus CTD-ILD patients (67% vs. 14%, p = .02). Two patients had severe respiratory distress that led to death for one of them. The course was favorable for the others, with a good response to steroids. The course tended to be more favorable for IPAF patients than for those with CTD-ILD (0% lung fibrosis in the IPAF group vs. 43% in the CTD-ILD group, p = .07).

CONCLUSION

We confirmed the existence of IPAF in children. Its prevalence was lower than in adults but comparable to that found for other pediatric series. Boys were more highly represented than in CTD-ILD. The course was favorable for most cases. Larger and more prospective studies are needed to confirm these results.

[Interstitial pneumonia with autoimmune features: monocentric prospective study]

AIM

To study demographic, clinical, serological and morphological features of interstitial pneumonia with autoimmune features (IPAF), compare survival in IPAF and interstitial lung disease in connective tissue diseases (CTD-ILD), and identify predictors of mortality and transformation to CTD in the IPAF group.

MATERIALS AND METHODS

The IPAF group included 48 patients (75.0% women, median age 57.5 years), CTD-ILD - 49 patients (79.6% women, median age 60.0 years). The analysis of demographic, clinical, laboratory and instrumental data was performed, as well as comparison of survival with the Kaplan-Meier method and the log-rank test in the IPAF and CTD-ILD groups. In the IPAF group, predictors of mortality and the development of CTD were studied with multivariate regression analysis.

RESULTS

Duration of observation period did not differ significantly in the IPAF and CTD-ILD groups (40.0 and 37.0 months, respectively). Clinical criteria of IPAF were observed in 25 (52.1%) patients, serological - in 44 (91.7%), morphological - in 44 (91.7%). Mortality in the IPAF group was significantly higher than in the CTD-ILD group (29.2 and 6.1%, respectively; p=0.023). The presence of diabetes mellitus, CT-pattern of usual interstitial pneumonia, and an initial low forced vital capacity value were independent predictors of mortality in the IPAF group. During the observation period, the development of CTD was noted in 4 (8.3%) patients with IPAF. The independent predictor of the CTD development was the increased C-reactive protein level.

CONCLUSION

IPAF is characterized by a lower survival rate compared to CTD-ILD, and a relatively low risk of CTD transformation.

[Interstitial Lung Disease]

Diffuse interstitial lung diseases (ILD) are a heterogeneous group of respiratory disorders that are usually classified together because they have similar clinical, radiological, physiological or pathological manifestations. In the last decade there have been important scientific advances in the study of these entities, which has led to a better understanding of their pathophysiology and to the appearance of treatments that have brought about a paradigm shift in the disease. This document presents a series of questions and answers on ILD, with special emphasis on the most relevant changes in terms of pathophysiology, diagnosis, and treatment.

Recurrent Exacerbations and Evolution into Polymyositis in a Patient with Interstitial Pneumonia with Autoimmune Features: A Case Report and Literature Review

Interstitial pneumonia with autoimmune features (IPAF) is a new disease entity proposed in 2015. Numerous questions regarding IPAF require clarification, including diagnostic criteria, standard managements for stable disease and exacerbation, and prognosis. We report a case of a 67-year-old Asian woman who presented with progressive dyspnea. Chest computed tomography (CT) scans revealed nonspecific interstitial pneumonia. Serologic testing indicated positive anti-Jo-1 without presence of extrathoracic manifestations. An IPAF diagnosis was made after a multidisciplinary discussion. The patient experienced a severe exacerbation requiring mechanical ventilation, and she was successfully salvaged with methylprednisolone pulse therapy and single-dose cyclophosphamide. During the one-year follow-up, she reported bilateral leg muscle weakness with noticeably elevated serum creatine kinase, suggesting polymyositis. The development of malignancy was also noted 15 months after the initial presentation, and the patient eventually died. This report demonstrated successful salvage treatment with glucocorticoid pulse therapy for IPAF with acute exacerbation. However, the maintenance therapy failed to control disease progression. The treatment strategies for exacerbation and stable disease in IPAF remain unknown and need further studies. Given the high risk of evolution into a defined connective tissue disease (CTD), regular evaluation of the clinical features and biomarkers of CTDs is essential for patients with IPAF.

Fine-tuning characterization of patients with interstitial pneumonia and an underlying autoimmune disease in real-world practice: We get closer with Nailfold videocapillaroscopy

Objectives

To assess performance of interstitial pneumonia (IP) with autoimmune features (IPAF) criteria in clinical practice and describe the utility of additional workup in identifying patients with underlying connective tissue diseases (CTD).

Methods

We set a retrospective study of our patients with autoimmune IP, who were allocated to CTD-IP, IPAF or undifferentiated autoimmune IP (uAIP) subgroups according to the updated classification criteria. Presence of the process-related variables comprising IPAF defining domains was scrutinized in all patients, and, when available, the results of nailfold videocapillaroscopy (NVC) were recorded.

Results

Thirty nine out of 118 patients, accounting for 71% of former undifferentiated cases, fulfilled IPAF criteria. Arthritis and Raynaud's phenomenon were prevalent in this subgroup. While systemic sclerosis-specific autoantibodies were restricted to CTD-IP patients, anti-tRNA synthetase antibodies were also present in IPAF. In contrast, rheumatoid factor, anti-Ro antibodies and ANA nucleolar patterns could be found in all subgroups. Usual interstitial pneumonia (UIP) / possible UIP were the most frequently observed radiographic patterns Therefore, the presence of thoracic multicompartimental findings as also performance of open lung biopsies were useful in characterizing as IPAF those UIP cases lacking a clinical domain. Interestingly, we could observe NVC abnormalities in 54% of IPAF and 36% of uAIP tested patients, even though many of them did not report Raynaud's phenomenon.

Conclusion

Besides application of IPAF criteria, distribution of IPAF defining variables along with NVC exams help identify more homogeneous phenotypic subgroups of autoimmune IP of potential relevance beyond clinical diagnosis.

Research progress of single-cell transcriptome sequencing in autoimmune diseases and autoinflammatory disease: A review

Autoimmunity refers to the phenomenon that the body's immune system produces antibodies or sensitized lymphocytes to its own tissues to cause an immune response. Immune disorders caused by autoimmunity can mediate autoimmune diseases. Autoimmune diseases have complicated pathogenesis due to the many types of cells involved, and the mechanism is still unclear. The emergence of single-cell research technology can solve the problem that ordinary transcriptome technology cannot be accurate to cell type. It provides unbiased results through independent analysis of cells in tissues and provides more mRNA information for identifying cell subpopulations, which provides a novel approach to study disruption of immune tolerance and disturbance of pro-inflammatory pathways on a cellular basis. It may fundamentally change the understanding of molecular pathways in the pathogenesis of autoimmune diseases and develop targeted drugs. Single-cell transcriptome sequencing (scRNA-seq) has been widely applied in autoimmune diseases, which provides a powerful tool for demonstrating the cellular heterogeneity of tissues involved in various immune inflammations, identifying pathogenic cell populations, and revealing the mechanism of disease occurrence and development. This review describes the principles of scRNA-seq, introduces common sequencing platforms and practical procedures, and focuses on the progress of scRNA-seq in 41 autoimmune diseases, which include 9 systemic autoimmune diseases and autoinflammatory diseases (rheumatoid arthritis, systemic lupus erythematosus, etc.) and 32 organ-specific autoimmune diseases (5 Skin diseases, 3 Nervous system diseases, 4 Eye diseases, 2 Respiratory system diseases, 2 Circulatory system diseases, 6 Liver, Gallbladder and Pancreas diseases, 2 Gastrointestinal system diseases, 3 Muscle, Bones and joint diseases, 3 Urinary system diseases, 2 Reproductive system diseases). This review also prospects the molecular mechanism targets of autoimmune diseases from the multi-molecular level and multi-dimensional analysis combined with single-cell multi-omics sequencing technology (such as scRNA-seq, Single cell ATAC-seq and single cell immune group library sequencing), which provides a reference for further exploring the pathogenesis and marker screening of autoimmune diseases and autoimmune inflammatory diseases in the future.

Some take-home messages from the 9th International Meeting on Pulmonary Rare Diseases and Orphan Drugs

Dissemination of updated knowledge on rare and ultra-rare respiratory diseases has always been a priority of the European Respiratory Review (ERR) [1, 2]. In this issue, we publish the first of a collection of four articles that discuss hot topics with direct practical clinical consequences. First, Mackintoshet al. [3] review the challenges and controversies (which are not few!) in “interstitial pneumonia with autoimmune features” (IPAF). Following the publication, in 2015, of the classification of IPAF proposed by the European Respiratory Society (ERS) and the American Thoracic Society (ATS) [4], a number of articles have been published on this entity which truly requires a multidisciplinary approach. Airway and vascular involvement are discussed in detail, as well as the problem of severe vasculopathy that can characterise some IPAF patients. The authors also discuss the controversial issue of the therapeutic approach for this “research entity” and state that “while identification of a histological NSIP pattern would support an immunosuppressive approach, histological confirmation of a UIP pattern would lead to a more cautious approach to immunosuppression, with frequent monitoring and earlier consideration of anti-fibrotic therapy, should there be progression” [3].

The 9th International Meeting on Pulmonary Rare Diseases and Orphan Drugs was dedicated to the management of rare pulmonary parenchymal and vascular diseases and rare variants of more common respiratory conditionshttps://bit.ly/3rq7b95