Review of Pulmonary Manifestations in Antisynthetase Syndrome

Antisynthetase syndrome (ASyS) is now a widely recognized entity within the spectrum of idiopathic inflammatory myopathies. Initially described in patients with a triad of myositis, arthritis, and interstitial lung disease (ILD), its presentation can be diverse. Additional common symptoms experienced by patients with ASyS include Raynaud's phenomenon, mechanic's hand, and fever. Although there is a significant overlap with polymyositis and dermatomyositis, the key distinction lies in the presence of antisynthetase antibodies (ASAs). Up to 10 ASAs have been identified to correlate with a presentation of ASyS, each having manifestations that may slightly differ from others. Despite the proposal of three classification criteria to aid diagnosis, the heterogeneous nature of patient presentations poses challenges. ILD confers a significant burden in patients with ASyS, sometimes manifesting in isolation. Notably, ILD is also often the initial presentation of ASyS, requiring pulmonologists to remain vigilant for an accurate diagnosis. This article will comprehensively review the various aspects of ASyS, including disease presentation, diagnosis, management, and clinical course, with a primary focus on its pulmonary manifestations.

A Review of Antisynthetase Syndrome-Associated Interstitial Lung Disease

Our objective in this review article is to present a clinical case of a patient with antisynthetase syndrome (ASyS) and provide an overview of the pathogenesis, classification criteria, antibody profiles, clinical features, and current knowledge of treatment options, focusing on interstitial lung disease (ILD). ASyS is an uncommon autoimmune disease with a heterogenous clinical presentation characterized by the presence of autoantibodies against an aminoacyl-tRNA synthetase and manifested by myositis, fever, inflammatory arthritis, Raynaud's phenomenon, mechanics hands, and ILD. ASyS-associated ILD (ASyS-ILD) is the most serious complication of ASyS, which may evolve to rapidly progressive ILD; therefore, it often requires thorough clinical and radiologic evaluation including recognition of a specific clinical phenotype associated with the antisynthetase antibodies (ASAbs) to guide therapeutic interventions.

New aspects of clinical and immunological characteristics in patients with anti-asparaginyl tRNA synthetase (anti-KS) autoantibody

OBJECTIVES

Anti-asparaginyl tRNA synthetase (anti-KS) antibody is present in patients with interstitial lung disease (ILD) accompanied by polymyositis/dermatomyositis. We examined clinical/immunological features of these patients.

METHODS

Polymyositis/dermatomyositis or ILD patients were screened for autoantibodies, and clinical/immunological data were collected retrospectively. ILD was diagnosed by computed tomography, and clinical/immunological features of anti-KS-positive patients were compared with those of anti-Jo-1-positive patients.

RESULTS

Sixteen anti-KS-positive patients [female = 11; male = 5; average age 63.6 years (range, 40-81) years] were diagnosed: seven had ILD, four had clinically amyopathic DM (CADM) and ILD, three had Sjögren's syndrome (SS) and ILD one each had rheumatoid arthritis and ILD, or CADM/SS overlap and ILD. All patients had ILD with chronic onset and clinical course; 11/16 (69%) had nonspecific interstitial pneumonia, and five (31%) had usual interstitial pneumonia pattern. Regarding skin manifestations, 4 (27%) had typical DM rash and 11 (69%) had mechanic's hands. All anti-KS-positive patients had no clinical muscle weakness or serum creatine kinase elevation; 8/16 patients (50%) had sicca symptoms at a significantly high frequency compared with anti-Jo-1-positive patients (50% vs 11%, P = 0.01).

CONCLUSIONS

Anti-KS-positive patients might form a distinguishable subset closely associated with sicca symptoms, CADM and chronic-type ILD with a relatively favourable prognosis.

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.

Fulminant Respiratory Failure Caused by Anti-asparaginyl tRNA Synthetase (Anti-KS) Antibody Syndrome-related Interstitial Lung Disease

Anti-asparaginyl transfer RNA (tRNA) synthetase (KS) antibodies, detected in <5% patients with anti-aminoacyl-tRNA synthetase antibody syndrome, are strongly associated with interstitial pneumonia but not myositis and skin symptoms. A recent report suggested that most patients with interstitial pneumonia and anti-KS antibody (KS-ILD) may present with chronic disease. We herein report a rare case of severe acute respiratory failure in a KS-ILD patient requiring extracorporeal membrane oxygenation (ECMO). ECMO is useful for facilitating not only lung rest until recovery but also the definitive diagnosis and treatment of ILD. KS-ILD can develop acutely with fulminant respiratory failure, as observed in this case.

Pulmonary histopathology of interstitial lung disease associated with antisynthetase antibodies

BACKGROUND

We aimed to determine if antibody type is an indicator of pulmonary histopathology, using antisynthetase antibody positive interstitial lung disease (ILD) cases with lung biopsy or autopsy findings.

METHODS

We conducted a comprehensive review of the English language literature in PubMed to identify ILD histopathology results for cases with antibodies against anti-aminoacyl-transfer RNA (tRNA) synthetases (anti-ARS antibodies), including Jo1, PL-12, PL-7, KS, ES, and OJ. We additionally identified patients who had ILD, anti-ARS antibodies, and a lung biopsy between 2015 and 2020 at Beth Israel Deaconess Medical Center. For each case, we documented the specific anti-ARS antibody and major histopathologic patterns identified on biopsy or autopsy, including usual interstitial pneumonia (UIP), nonspecific interstitial pneumonia (NSIP), organizing pneumonia (OP), and acute lung injury (ALI). To determine if histopathology varied by antibody type, we compared the proportion of each of four major patterns by antibody type using the Fisher's Exact test.

RESULTS

We identified 310 cases with pathology findings and anti-ARS antibody positivity, including 12 cases from our institution. The proportion of NSIP differed significantly across antibody type, found in 31% of Jo1 (p < 0.01), 67% of EJ (p < 0.01), and 63% of KS (p < 0.01) cases. OP was common in Jo1 (23%, p = 0.07), but rare in EJ (4%, p = 0.04) and KS (4%, p = 0.04). UIP was common in PL-12 alone (36%, p = 0.03).

CONCLUSION

The frequency of histopathologic findings in ILD with anti-ARS positivity varies significantly by antibody type, and NSIP occurs in less than half of all cases.

A Master Autoantigen-ome Links Alternative Splicing, Female Predilection, and COVID-19 to Autoimmune Diseases

Chronic and debilitating autoimmune sequelae pose a grave concern for the post-COVID-19 pandemic era. Based on our discovery that the glycosaminoglycan dermatan sulfate (DS) displays peculiar affinity to apoptotic cells and autoantigens (autoAgs) and that DS-autoAg complexes cooperatively stimulate autoreactive B1 cell responses, we compiled a database of 751 candidate autoAgs from six human cell types. At least 657 of these have been found to be affected by SARS-CoV-2 infection based on currently available multi-omic COVID data, and at least 400 are confirmed targets of autoantibodies in a wide array of autoimmune diseases and cancer. The autoantigen-ome is significantly associated with various processes in viral infections, such as translation, protein processing, and vesicle transport. Interestingly, the coding genes of autoAgs predominantly contain multiple exons with many possible alternative splicing variants, short transcripts, and short UTR lengths. These observations and the finding that numerous autoAgs involved in RNA-splicing showed altered expression in viral infections suggest that viruses exploit alternative splicing to reprogram host cell machinery to ensure viral replication and survival. While each cell type gives rise to a unique pool of autoAgs, 39 common autoAgs associated with cell stress and apoptosis were identified from all six cell types, with several being known markers of systemic autoimmune diseases. In particular, the common autoAg UBA1 that catalyzes the first step in ubiquitination is encoded by an X-chromosome escape gene. Given its essential function in apoptotic cell clearance and that X-inactivation escape tends to increase with aging, UBA1 dysfunction can therefore predispose aging women to autoimmune disorders. In summary, we propose a model of how viral infections lead to extensive molecular alterations and host cell death, autoimmune responses facilitated by autoAg-DS complexes, and ultimately autoimmune diseases. Overall, this master autoantigen-ome provides a molecular guide for investigating the myriad of autoimmune sequalae to COVID-19 and clues to the rare but reported adverse effects of the currently available COVID vaccines.

An Autoantigen-ome from HS-Sultan B-Lymphoblasts Offers a Molecular Map for Investigating Autoimmune Sequelae of COVID-19

To understand how COVID-19 may induce autoimmune diseases, we have been compiling an atlas of COVID-autoantigens (autoAgs). Using dermatan sulfate (DS) affinity enrichment of autoantigenic proteins extracted from HS-Sultan lymphoblasts, we identified 362 DS-affinity proteins, of which at least 201 (56%) are confirmed autoAgs. Comparison with available multi-omic COVID data shows that 315 (87%) of the 362 proteins are affected in SARS-CoV-2 infection via altered expression, interaction with viral components, or modification by phosphorylation or ubiquitination, at least 186 (59%) of which are known autoAgs. These proteins are associated with gene expression, mRNA processing, mRNA splicing, translation, protein folding, vesicles, and chromosome organization. Numerous nuclear autoAgs were identified, including both classical ANAs and ENAs of systemic autoimmune diseases and unique autoAgs involved in the DNA replication fork, mitotic cell cycle, or telomerase maintenance. We also identified many uncommon autoAgs involved in nucleic acid and peptide biosynthesis and nucleocytoplasmic transport, such as aminoacyl-tRNA synthetases. In addition, this study found autoAgs that potentially interact with multiple SARS-CoV-2 Nsp and Orf components, including CCT/TriC chaperonin, insulin degrading enzyme, platelet-activating factor acetylhydrolase, and the ezrin-moesin-radixin family. Furthermore, B-cell-specific IgM-associated ER complex (including MBZ1, BiP, heat shock proteins, and protein disulfide-isomerases) is enriched by DS-affinity and up-regulated in B-cells of COVID-19 patients, and a similar IgH-associated ER complex was also identified in autoreactive pre-B1 cells in our previous study, which suggests a role of autoreactive B1 cells in COVID-19 that merits further investigation. In summary, this study demonstrates that virally infected cells are characterized by alterations of proteins with propensity to become autoAgs, thereby providing a possible explanation for infection-induced autoimmunity. The COVID autoantigen-ome provides a valuable molecular resource and map for investigation of COVID-related autoimmune sequelae and considerations for vaccine design.

Interstitial lung disease is a major characteristic of anti-KS associated ant-synthetase syndrome

Background:

Anti-KS autoantibodies are rare myositis-specific autoantibodies that have been described to target asparaginyl-transfer RNA synthetase.

Methods:

Here, we review the published literature on critical issues concerning the detection of anti-KS antibodies and the clinical features associated with their presence.

Results:

Seven articles are reviewed, in all of which immunoprecipitation was employed for the detection of anti-KS antibodies. A total of 47 patients were included; the ratio of females to males was 1.9:1. In total, 46 (98%) of these patients had interstitial lung disease (ILD), which was the sole manifestation in half (50%) of them. Pulmonary pathology revealed 7 (27%) with usual interstitial pneumonia, and 16 (62%) with non-specific pneumonia. Arthritis was present in about one-quarter (26%) of patients, and the incidence of Raynaud’s phenomenon and mechanic’s hands was 19% and 32%, respectively. However, manifestations of myositis were rare (9%). In addition, three (11%) patients had malignant tumors. Most patients responded to glucocorticoid therapy.

Conclusions:

Identifying anti-KS in patients with ILD may be useful for treatment, but reliable practical detection is needed. Furthermore, clinicians need to be aware of the possible presence of anti-KS antibodies in patients with ILD, either isolated or in combination with myositis.

Prevalence of Novel Myositis Autoantibodies in a Large Cohort of Patients with Interstitial Lung Disease

Connective tissue diseases (CTDs) are an important secondary cause of interstitial lung disease (ILD). If a CTD is suspected, clinicians are recommended to perform autoantibody testing, including for myositis autoantibodies. In this study, the prevalence and clinical associations of novel myositis autoantibodies in ILD are presented. A total of 1194 patients with ILD and 116 healthy subjects were tested for antibodies specific for Ks, Ha, Zoα, and cN1A with a line-blot assay on serum available at the time of diagnosis. Autoantibodies were demonstrated in 63 (5.3%) patients and one (0.9%) healthy control (p = 0.035). Autoantibodies were found more frequently in females (p = 0.042) and patients without a histological and/or radiological usual interstitial pneumonia (UIP; p = 0.010) and a trend towards CTD-ILDs (8.4%) was seen compared with other ILDs (4.9%; p = 0.090). The prevalence of antibodies specific for Ks, Ha, Zoα, and cN1A was, respectively, 1.3%, 2.0%, 1.4%, and 0.9% in ILD. Anti-Ha and Anti-Ks were observed in males with unclassifiable idiopathic interstitial pneumonia (unclassifiable IIP), hypersensitivity pneumonitis (HP), and various CTD-ILDs, whereas anti-cN1A was seen in females with antisynthetase syndrome (ASS), HP, and idiopathic pulmonary fibrosis (IPF). Anti-Zoα was associated with CTD-ILD (OR 2.5; 95%CI 1.11-5.61; p = 0.027). In conclusion, a relatively high prevalence of previously unknown myositis autoantibodies was found in a large cohort of various ILDs. Our results contribute to the awareness that circulating autoantibodies can be found in ILDs with or without established CTD. Whether these antibodies have to be added to the standard set of autoantibodies analysed in conventional myositis blot assays for diagnostic purposes in clinical ILD care requires further study.

Pulmonary involvement in antisynthetase syndrome

PURPOSE OF REVIEW

Lung involvement is a distinctive feature of antisynthetase syndrome (ASS) and it is considered a basic disease-classifying criterion. In this review, we go over clinical features, radiological patterns, prognostic factors, pathogenesis and treatment of lung involvement in ASS patients, focusing on the clinical differences linked to the different antibody specificities known so far.

RECENT FINDINGS

The lung is the most common extramuscular organ involved in ASS and has the greatest impact on patient prognosis. The pulmonary disease-defining manifestation in ASS is interstitial lung disease (ILD), yet a proportion of patients also develop pulmonary arterial hypertension and, less frequently, obstructive bronchiolitis or acute respiratory failure according to drivers not yet fully understood but likely associated with the underlying autoantibody pattern. Clinical presentation of pulmonary involvement can range from milder forms to a rapidly progressive disease which may lead to chronic lung damage if misdiagnosed and not properly treated.

SUMMARY

The knowledge of risk factors associated with progressive or refractory lung damage is important to identify and properly treat patients with the poorest prognosis. For those with a disease not responsive to conventional therapy the efficacy of other therapeutic option is under evaluation.

Clinical manifestations and treatment of antisynthetase syndrome

Antisynthetase syndrome (ASyS) is an autoimmune disease clinically manifested most often by interstitial lung disease, myositis, and arthritis. Raynaud's syndrome, fever, and rashes are also commonly seen. This syndrome is characterized by the highly specific presence of antibodies against various aminoacyl transfer RNA synthetases, including Jo-1 and others. In this chapter, we provide an overview of ASyS, including pathogenesis, common clinical manifestations, and treatment strategies. We discuss the spectrum of disease seen with specific antisynthetase antibodies and examine the differences in phenotype between patients with different antisynthetase antibodies. We outline common treatment strategies, which should generally target the most severe and life- or organ-threatening disease manifestations. Finally, we discuss short- and long-term prognosis in ASyS.

Clinical, radiological, and pathological features of anti-asparaginyl tRNA synthetase antibody-related interstitial lung disease

BACKGROUND

Myositis and interstitial lung disease (ILD) frequently occur in patients with anti-aminoacyl-tRNA synthetase (ARS) antibodies. Nearly half of ARS-ILD patients have the acute or subacute form of the disease, and one-third of these patients show a deterioration in pulmonary function over the long-term course because of frequent recurrences and refractoriness to therapy. Several reports recently described different characteristics depending on the individual anti-ARS antibodies, and the anti-asparaginyl tRNA synthetase (KS) antibody was strongly linked to ILD rather than to myositis. We therefore hypothesized that KS-ILD may have clinical characteristics that differ from those of other ARS-ILDs. The aim of this study was to clarify the clinical, radiological, and pathological features of KS antibody-positive ILD.

METHODS

We retrospectively analyzed 19 consecutive patients with KS-ILD who underwent initial clinical measurements and high-resolution computed tomography and pathological assessments. We also analyzed disease behavior based on pulmonary function test results during the follow-up period.

RESULTS

Our KS-ILD cohort included patients with dermatomyositis (10.5%), primary Sjögren syndrome (5.3%), and idiopathic ILD (84.2%). Most patients presented with chronic onset (89.5%) and a nonspecific pattern of interstitial pneumonia at each radiological and pathological assessment (89.4% and 85.7%, respectively). The pulmonary function test results showed that the mean changes from the initial %forced vital capacity and %diffusing capacity of the lung for carbon monoxide at 3 years were 3.7% ± 2.9% and 9.35% ± 3.0%, respectively.

CONCLUSIONS

Most KS-ILD patients showed a tendency for chronic disease onset and long-term stabilization of pulmonary function.

Unique N-terminal extension domain of human asparaginyl-tRNA synthetase elicits CCR3-mediated chemokine activity

Asparaginyl-tRNA synthetase (NRS) is not only essential in protein translation but also associated with autoimmune diseases. Particularly, patients with antibodies that recognize NRS often develop interstitial lung disease (ILD). However, the underlying mechanism of how NRS is recognized by immune cells and provokes inflammatory responses is not well-understood. Here, we found that the crystal structure of the unique N-terminal extension domain of human NRS (named as UNE-N, where -N denotes NRS) resembles that of the chemotactic N-terminal domain of NRS from a filarial nematode, Brugia malayi, which recruits and activates specific immune cells by interacting with CXC chemokine receptor 1 and 2. UNE-N induced migration of CC chemokine receptor 3 (CCR3)-expressing cells. The chemokine activity of UNE-N was significantly reduced by suppressing CCR3 expression with CCR3-targeting siRNA, and the loop3 region of UNE-N was shown to interact mainly with the extracellular domains of CCR3 in nuclear magnetic resonance perturbation experiments. Based on these results, evolutionarily acquired UNE-N elicits chemokine activities that would promote NRS-CCR3-mediated proinflammatory signaling in ILD.

Myositis-associated usual interstitial pneumonia has a better survival than idiopathic pulmonary fibrosis

Objective

To compare the survival outcomes between myositis-associated usual interstitial pneumonia (MA-UIP) and idiopathic pulmonary fibrosis (IPF-UIP).

Methods

Adult MA-UIP and IPF-UIP patients were identified using CTD and IPF registries. The MA-UIP cohort included myositis or anti-synthetase syndrome patients with interstitial lung disease while manifesting UIP on high-resolution CT chest and/or a lung biopsy revealing UIP histology. IPF subjects met American Thoracic Society criteria and similarly had UIP histopathology. Kaplan-Meier survival curves compared cumulative and pulmonary event-free survival (event = transplant or death) between (i) all MA-UIP and IPF-UIP subjects, (ii) MA-UIP with biopsy proven UIP (n = 25) vs IPF-UIP subjects matched for age, gender and baseline forced vital capacity (±10%). Cox proportional hazards ratios compared the survival controlling for co-variates.

Results

Eighty-one IPF-UIP and 43 MA-UIP subjects were identified. The median cumulative and event-free survival time in IPF vs MA-UIP was 5.25/1.8 years vs 16.2/10.8 years, respectively. Cumulative and event-free survival was significantly worse in IPF-UIP vs MA-UIP [hazards ratio of IPF-UIP was 2.9 (95% CI: 1.5, 5.6) and 5.0 (95% CI: 2.8, 8.7) (P < 0.001), respectively]. IPF-UIP event-free survival (but not cumulative) remained significantly worse than MA-UIP with a hazards ratio of 6.4 (95% CI: 3.0, 13.8) after controlling for age at interstitial lung disease diagnosis, gender, ethnicity and baseline forced vital capacity%. Respiratory failure was the most common cause of death in both groups. A sub-analysis of 25 biopsy-proven MA-UIP subjects showed similar results.

Conclusion

MA-UIP patients demonstrated a significant survival advantage over a matched IPF cohort, suggesting that despite similar histological and radiographic findings at presentation, the prognosis of MA-UIP is superior to that of IPF-UIP.