Interstitial Pneumonia with Autoimmune Features: Overview of proposed criteria and recent cohort characterization

[The concept of interstitial pneumonia with autoimmune features (IPAF)]

Interstitial lung diseases (ILD) are a heterogeneous group of respiratory diseases often related to connective tissue diseases. Some patients will develop an ILD with autoimmune features without reaching the recommended criteria for autoimmune diseases. Their management is difficult because they have both features for idiopathic and connective tissue disease. To better identify these patients, the concept of interstitial pneumonia with autoimmune features (IPAF) has been created. The diagnosis relies on ILD without identified cause and the presence of at least one defined criterion among 2 of the 3 following domains: clinic, serologic, and morphologic. The mean age at diagnosis is 60, a sex ratio of 1/1, and depending on the authors close to 20% of patients with IPAF will develop a connective tissue disease according to the international criterion. Their prognosis is better than for patients with idiopathic ILD and with an average 5-year survival of 70%. Older age at diagnosis, a pattern of usual interstitial pneumonia, and an impaired diffusing capacity for carbon monoxide have been identified as poor prognosis factors. The treatment relies on usual care for chronic respiratory diseases and is often associated with immunosuppressive and/or antifibrotic therapies. The objective of this classification is to better characterize these patients and improve their management.

Interstitial lung diseases associated with ANCA positivity: A different disease spectrum from interstitial pneumonia with autoimmune features

BACKGROUND

Anti-neutrophil cytoplasmic antibody (ANCA) is a type of autoantibodies associated with vasculitis. ANCA positivity is commonly observed in interstitial lung disease (ILD) patients. 7%-10% of ANCA-positive ILD patients don't present any symptoms of systemic vasculitis and are termed ANCA-positive idiopathic interstitial pneumonia (ANCA-IIP). Some researchers propose that ANCA-IIP should be categorized as interstitial pneumonia with autoimmune features (IPAF), although the official ATS/ERS statements exclude ANCA-IIP from this classification. Whether ANCA-IIP should be categorized into the entity of IPAF is still debatable.

METHODS

Patients diagnosed with ANCA-IIP and those with IPAF were analyzed in a retrospective study of ILD. The clinical outcomes were determined through pulmonary function tests (PFTs) after a one-year follow-up, as well as assessing all-cause mortality.

RESULTS

27 patients with ANCA-IIP and 143 patients with IPAF were analyzed from a cohort of 995 patients with ILD. Patients in the ANCA-IIP group had an older age and a high proportion of males compared to those in the IPAF group. PFT results at baseline were similar between the two groups, except for a better FEV1% in the ANCA-IIP group. Glucocorticoid and immunosuppressive therapy improved pulmonary function in patients with IPAF, but it continued to deteriorate after one year of treatment in the ANCA-IIP group. Furthermore, the all-cause mortality rate was significantly higher in the ANCA-IIP group than in the IPAF group (22.2% vs. 6.3%, P = 0.017).

CONCLUSION

The responses to glucocorticoid and immunosuppressive therapy differ between the ANCA-IIP and IPAF groups, leading to divergent prognoses. Therefore, it is inappropriate to classify ANCA-IIP as part of IPAF.

Connective tissue disease-related interstitial lung disease (CTD-ILD) and interstitial lung abnormality (ILA): Evolving concept of CT findings, pathology and management

Connective tissue diseases (CTDs) demonstrating features of interstitial lung disease (ILD) include systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), systemic sclerosis (SSc), dermatomyositis (DM) and polymyositis (PM), ankylosing spondylitis (AS), Sjogren syndrome (SS), and mixed connective tissue disease (MCTD). On histopathology of lung biopsy in CTD-related ILDs (CTD-ILDs), multi-compartment involvement is an important clue, and when present, should bring CTD to the top of the list of etiologic differential diagnoses. Diverse histologic patterns including nonspecific interstitial pneumonia (NSIP), usual interstitial pneumonia (UIP), organizing pneumonia, apical fibrosis, diffuse alveolar damage, and lymphoid interstitial pneumonia can be seen on histology in patients with CTD-ILDs. Although proportions of ILDs vary, the NSIP pattern accounts for a large proportion, especially in SSc, DM and/or PM and MCTD, followed by the UIP pattern. In RA patients, interstitial lung abnormality (ILA) is reported to occur in approximately 20–60% of individuals of which 35–45% will have progression of the CT abnormality. Subpleural distribution and greater baseline ILA involvement are risk factors associated with disease progression. Asymptomatic CTD-ILDs or ILA patients with normal lung function and without evidence of disease progression can be followed without treatment. Immunosuppressive or antifibrotic agents for symptomatic and/or fibrosing CTD-ILDs can be used in patients who require treatment.

Acute myocarditis with autoimmune features: one-year follow-up with CMR

In this prospective study on patients with acute myocarditis (AM), we aimed to describe the new concept of AMAF (AM with autoimmune features) similar to the previously described interstitial pneumonia with autoimmune features (IPAF). IPAF has recently emerged as a new entity, and IPAF patients appear to have fewer episodes of exacerbation and better survival than patients with idiopathic pulmonary fibrosis. Consecutive patients with infarct-like CMR-confirmed AM were classified AMAF if their serologic status measured from blood sampled at presentation was positive (antinuclear antibodies (ANA) ≥ 1:320), but without meeting established classification criteria for connective tissue disease (CTD). The myocardial tissue abnormalities and their progression were assessed on cardiac magnetic resonance (CMR) within 7 days following symptom onset and at 1 year according to their seropositivity. Among the 64 AM patients included, seven presented AMAF (11%). At baseline CMR, patients with AMAF had half as much late gadolinium enhancement (LGE) as seronegative AM patients (4.41% (1.47-4.41) of myocardial volume versus 8.82% (5.88-14.71), p = 0.01, respectively). At 1-year of follow-up, persistent myocardial scarring was less frequent in AMAF patients (n = 2 (28.6%) than seronegative AM patients (n = 38 (66.7%) (p = 0.021). AMAF, diagnosed as seropositive AM without a specific autoimmune disease, is not rare and is associated with less extensive LGE in the acute phase. In addition, AMAF patients had more favorable outcomes on 12-month CMR. Prospective studies are needed to address the clinical significance of this new concept and its long-term cardiovascular impact.

Interstitial pneumonia with autoimmune features: from research classification to diagnosis

PURPOSE OF REVIEW

The term interstitial pneumonia with autoimmune features (IPAF) was first proposed by an international task force in 2015 as a research classification to standardise nomenclature regarding patients with idiopathic interstitial pneumonia and features of connective tissue disease. However, how the use of this term and its proposed definition translates to clinical practice remains uncertain. This review will provide a comprehensive overview of studies of IPAF cohorts to date, discuss the consideration of IPAF as a distinct diagnostic entity and outline a suggested approach to patient management.

RECENT FINDINGS

Considerable heterogeneity exists between published IPAF cohorts, with some cohorts exhibiting similarities to those with connective tissue disease-associated interstitial lung disease (CTD-ILD), and others more similar to idiopathic interstitial pneumonias including idiopathic pulmonary fibrosis (IPF). Little data exist to inform the management of patients who fulfil the IPAF criteria. Preliminary data supports pragmatic management of these patients as having a working clinical diagnosis of either idiopathic interstitial pneumonia or CTD-ILD. Future research studies into this approach are required.

SUMMARY

The term IPAF, and its definition, have been of fundamental benefit to facilitating research in this diverse patient group. However, to date, there remain many unanswered questions regarding their natural histories and response to treatment.

Krebs von den Lungen-6 and surfactant protein-A in interstitial pneumonia with autoimmune features

Interstitial pneumonia with autoimmune features (IPAF) is a special subtype of interstitial lung disease that has received worldwide attention. Krebs von den Lungen-6 (KL-6) and surfactant protein-A (SP-A) can be used as an important biomarker of interstitial lung disease, but its exact relationship with IPAF is poorly understood.A total of 65 IPAF patients were included in the study and were followed up for 52 weeks. The KL-6 and SP-A were evaluated by chemiluminescence enzyme immunoassay. The above indicators were tested at 2 time points, baseline (the first admission of patients) and 52 weeks. We also collected the indicators of antinuclear antibodies and rheumatoid factor. Based on high-resolution computed tomography evaluations, patients were divided into: aggravation, stable, and improvement group. At same time, 30 age-matched normal people as normal control were recruited, the same information was collected. Correlations among the groups were compared and analyzed.The KL-6 and SP-A level in IPAF patients were significantly higher than normal controls (fold increase = 11.35 and 1.39, both P < .001) and differed significantly at baseline and 52 weeks in IPAF (difference ratio = 37.7% and 21.3%, P < .05, both). There were significant differences at baseline and 52 weeks (r values of aggravation, improvement, and stable groups for KL-6 were 0.705, 0.770, and 0.344, P = .001, .001, and .163, and for SP-A the r value were 0.672, 0.375, and 0.316, P = .001, .126, and .152). In aggravation group, KL-6 and SP-A were correlated with CT scores (both P < .05). Diffusing capacity of the lung for carbon monoxide (DLCO) and forced vital capacity (FVC), % predicted showed a progressive downward trend, with a significant difference at baseline and 52 weeks in IPAF patients (difference ratio = 23.8% and 20.6%, both P < .05). There was a significant correlation between KL-6 and FVC % predicted and DLCO (both P < .05), SP-A showed negatively correlated with DLCO, but not significantly correlated with FVC % predicted (P < .05 and .47).This study demonstrated that KL-6 and SP-A can reflect disease progression, and both 2 play a key role at reflection of lung epithelial cell injury and fibrosis degree in IPAF.

A major genetic determinant of autoimmune diseases is associated with the presence of autoantibodies in hypersensitivity pneumonitis

Background

Hypersensitivity pneumonitis is an immune-mediated disease triggered by exposure to organic particles in susceptible individuals. It has been reported that a subgroup of patients with hypersensitivity pneumonitis develops autoantibodies with or without clinical manifestations of autoimmune disease. However, the mechanisms involved in this process and the effect of the autoantibodies on clinical course in hypersensitivity pneumonitis is unknown. We evaluated the association between human leukocyte antigen (HLA) class II alleles and hypersensitivity pneumonitis patients with and without autoantibodies.

Methods

170 hypersensitivity pneumonitis patients were included. We analysed the presence of antinuclear antibodies, rheumatoid factor, anti-SSA/Ro, anti-SSB/La and anti-CCP at the time of diagnosis. In addition, in a subset of patients we evaluated anti-Scl-70, anti-neutrophil cytoplasmic antibody, and anti-DNA. HLA typing was performed using PCR sequence-specific primers in a high-resolution modality, including HLA-DRB1 and HLA-DQB1 loci. Statistical analysis was performed employing Epi-Info v7 and SPSS v20.

Results

60 hypersensitivity pneumonitis patients showed sera autoantibodies (HPAbs⁺), and 110 hypersensitivity pneumonitis patients did not (HPAbs⁻). The frequency of the allele HLA-DRB1*03:01 was remarkably increased in the HPAbs⁺ group (10.8% versus 0.45%; OR 30.14, 95% CI 3.83–237.1; p=1.65×10^-4 after Bonferroni's correction). Likewise, we found that the haplotype DRB1*03:01-DQB1*02:01, which is part of the 8.1 ancestral haplotype, a major genetic determinant of autoimmune diseases, confers significant risk to develop autoantibodies (OR 19.23, 95% CI 2.37–155.9; p=0.0088 after Bonferroni's correction). In addition, the HLA-DRB1*03:01 allele was associated with higher mortality in patients with hypersensitivity pneumonitis (adjusted OR 5.9, 95% CI 1.05–33.05; p=0.043).

Conclusions

A subset of hypersensitivity pneumonitis patients presents circulating autoantibodies and higher mortality that are associated with some alleles of 8.1 ancestral haplotype.

Alleles from 8.1 ancestral haplotype (#HLA-DRB1 and DQB1 loci) are associated with #autoantibodies production in #hypersensitivity #pneumonitis in a cohort of Mexican mestizo patientshttps://bit.ly/3bprPeB

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).

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.