New insights in myositis-specific autoantibodies

Association between anti-PL7 antibodies and increased fibrotic component in patients with antisynthetase syndrome and interstitial lung disease: a cross-sectional study

OBJECTIVE

To evaluate whether anti-PL7 and anti-PL12 autoantibodies are associated with a greater extent of the fibrotic component of ILD in ASSD patients.

METHODS

Patients with ILD-ASSD who were positive for one of the following autoantibodies: anti-Jo1, anti-PL7, anti-PL12, and anti-EJ were included. Clinical manifestations, CPK levels, pulmonary function tests, and HCRT assessments were prospectively collected according to the Goh index. The fibrotic, inflammatory, and overall extension of the Goh index and DLCO were assessed by multiple linear analyses and compared between ASSD antibody subgroups.

RESULTS

Sixty-six patients were included; 17 were positive for anti-Jo1 (26%), 17 for anti-PL7 (26%), 20 for anti-PL12 (30%), and 9 (14%) for anti-EJ. Patients with anti-PL7 and anti-PL12 had a more extensive fibrotic component than anti-Jo1. Anti-PL7 patients had a 7.9% increase in the fibrotic extension (cβ = 7.9; 95% CI 1.863, 13.918), and the strength of the association was not modified after controlling for sex, age, and time of disease evolution (aβ = 7.9; 95% CI 0.677, 15.076) and also was associated with an increase in ILD severity after adjusting for the same variables, denoted by a lower DLCO (aβ =  - 4.47; 95% CI - 8.919 to - 0.015).

CONCLUSIONS

Anti-PL7-positive ASSD patients had more extensive fibrosis and severe ILD than the anti-Jo1 subgroup. This information is clinically useful and has significant implications for managing these patients, suggesting the need for early consideration of concurrent immunosuppressive and antifibrotic therapy.

Prognostic significance of natural killer cell depletion in predicting progressive fibrosing interstitial lung disease in idiopathic inflammatory myopathies

Objectives

Interstitial lung disease (ILD) is one of the common extramuscular involvement in idiopathic inflammatory myopathies (IIMs) (1). Several patients develop a progressive fibrosing ILD (PF-ILD) despite conventional treatment, resulting in a progressive deterioration in their quality of life (2). Here, we investigated the clinical and immune characteristics of IIM-ILD and risk factors for PF-ILD in IIM, mainly in anti-melanoma differentiation-associated protein 5 (anti-MDA5+) dermatomyositis (DM) and anti-synthetase syndrome (ASS).

Methods

Here, a prospective cohort of 156 patients with IIM-ILD were included in the longitudinal analysis and divided into the PF-ILD (n=65) and non-PF-ILD (n=91) groups, and their baseline clinical characteristics were compared. Univariate and multivariate Cox analyses were performed to identify the variables significantly associated with pulmonary fibrosis progression in the total cohort, then anti-MDA5+ DM and ASS groups separately.

Results

Peripheral blood lymphocyte counts, including T, B, and NK cell counts, were significantly lower in the PF-ILD group than in the non-PF-ILD group. This characteristic is also present in the comparison between patients with anti-MDA5+ DM and ASS. The multivariate Cox regression analysis revealed that age > 43.5 years [HR: 7.653 (95% CI: 2.005-29.204), p = 0.003], absolute NK cell count < 148 cells/μL [HR: 6.277 (95% CI: 1.572-25.067), p = 0.009] and absolute Th cell count < 533.2 cells/μL [HR: 4.703 (95% CI: 1.014-21.821), p = 0.048] were independent predictors of progressive fibrosing during 1-year follow-up for patients with anti-MDA5+ DM, while absolute count of NK cells < 303.3 cells/µL [HR: 19.962 (95% CI: 3.108-128.223), p = 0.002], absolute count of lymphocytes < 1.545×109/L [HR: 9.684 (95% CI: 1.063-88.186), p = 0.044], and ferritin > 259.45 ng/mL [HR: 6 (95% CI: 1.116-32.256), p = 0.037] were independent predictors of PF-ILD for patients with ASS.

Conclusions

Patients with anti-MDA5+ DM and ASS have independent risk factors for PF-ILD. Lymphocyte depletion (particularly NK cells) was significantly associated with PF-ILD within 1-year of follow-up for IIM-ILD.

[Autoantibody diagnostics in idiopathic inflammatory myopathy]

Idiopathic inflammatory myopathy (IIM) is a group of rare and heterogeneous systemic diseases that manifest not only in the muscles but also in the skin, joints, and lungs. Initial symptoms can be isolated and variable and thus the diagnosis poses challenges to various specialist groups. As autoantibodies are sometimes the only specific findings that lead to the diagnosis and appropriate treatment, basic knowledge of them is essential. This article explains the available test systems, names the clinical indications necessary for the initiation of autoantibody diagnostics, provides information on the etymology, antigens, synonyms, and first descriptors, describes indirect immunofluorescence on HEp‑2 cells induced by myositis antibodies, and provides clinical-serological associations. The comparison of the autoantibody findings with the clinical symptoms and laboratory findings enables the identification of false positive or false negative laboratory findings in the sense of a plausibility check.

Clinicopathological Reclassification of Idiopathic Inflammatory Myopathy to Match the Serological Results of Myositis-Specific Antibodies

BACKGROUND AND PURPOSE

Advances in serological tests are transforming the classification of idiopathic inflammatory myopathy (IIM). The new criteria suggested by the 119th European Neuromuscular Center international workshop divide IIM cases into four main diseases according to clinical and pathological findings, adding immune-mediated necrotizing myositis and nonspecific myositis to the classic categories of polymyositis and dermatomyositis.

METHODS

Seventy one cases of IIM with sufficient available clinical and pathological data were reviewed to be reclassified according to the new criteria.

RESULTS

Most of the cases previously classified as polymyositis (77.8%, 35/45) were reclassified as immune-mediated necrotizing myopathy. The results of myositis-specific antibodies matched well with the new clinicopathological classification.

CONCLUSIONS

This new clinicopathological classification for IIM in combination with serological test results could be applied to our previous case series. Adoption of the new criteria will lead to a better understanding of the disease and hence new therapeutic insights.

Interstitial lung disease with and without progressive fibrosing phenotype in patients with idiopathic inflammatory myopathies: data from a large multicentric cohort

OBJECTIVES

Patients with connective tissue diseases can develop interstitial lung disease (ILD), leading to a progressive fibrosing ILD (PF-ILD) phenotype in some cases. We aimed to investigate the occurrence of PF-ILD in idiopathic inflammatory myopathies (IIMs), and factors potentially predicting this phenotype. Secondary aims were to assess the radiological pattern and factors associated with IIMs-ILD.

METHODS

Patients with IIMs from our multicentric prospective cohort were retrospectively evaluated. Data were recorded at IIMs and ILD diagnosis, and during follow-up. Patients with ILD were classified according to the predominant high-resolution CT (HRCT) pattern: non-specific interstitial pneumonia (NSIP), usual interstitial pneumonia (UIP) and organising pneumonia (OP). PF-ILD was defined according to the 2022 American Thoracic Society (ATS), European Respiratory Society (ERS), Japanese Respiratory Society (JRS) and Latin American Thoracic Society (ALAT) guidelines. Univariate and multivariate analyses were performed to identify factors associated to ILD and to PF-ILD.

RESULTS

Of 253 patients with IIMs, 125 (49%) had ILD: 99 (78%) at IIMs diagnosis and 26 (22%) during follow-up (21/26 within 5 years). Multivariate analysis identified anti-Jo-1, anti-MDA5, anti-Ro52, high score on manual muscle test, mechanic's hands and Raynaud's phenomenon as independently associated with ILD. The predominant HRCT pattern was NSIP (50% of patients), followed by UIP (28%) and OP (22%). At 1-year follow-up, PF-ILD occurred in 18% of IIMs-ILD. PF-ILD was predicted by anti-MDA5, heliotropic rash, xerostomia and xerophthalmia at univariate but not at multivariate analysis.

CONCLUSION

Patients with IIM should be carefully screened for ILD at IIMs diagnosis and yearly during follow-up. All patients with IIMs-ILD should be carefully monitored to capture ILD progression since a consistent proportion of them are expected to develop PF-ILD.

Jo-1 Antibodies From Myositis Induce Complement-Dependent Cytotoxicity and TREM-1 Upregulation in Muscle Endothelial Cells

BACKGROUND AND OBJECTIVES

Muscle microangiopathy due to dysfunction of endothelial cells because of inflammation is a critical hallmark of dermatomyositis (DM); however, its pathomechanism remains unclear. The aim of this study was to evaluate the effect of immunogloblin G (IgG) from patients with idiopathic inflammatory myopathies (IIM) on muscle endothelial cells in vitro.

METHODS

Using a high-content imaging system, we analyzed whether IgG purified from sera from patients with IIM (n = 15), disease controls (DCs: n = 7), and healthy controls (HCs: n = 7) can bind to muscle endothelial cells and induce complement-dependent cellular cytotoxicity.

RESULTS

IgGs from Jo-1 antibody myositis could bind to muscle endothelial cells and caused complement-dependent cell cytotoxicity. RNA-seq demonstrated the upregulation of genes associated with tumor necrosis factor (TNF)-α, triggering receptor expressed on myeloid cells-1 (TREM-1), CD25, and mitochondria pathways after exposure to IgG from the Jo-1, signal recognition particle (SRP), and polymyositis (PM) groups. The high-content imaging system showed that TREM-1 expression in the Jo-1, SRP, and PM groups was increased in comparison with DCs and HCs and that the TNF-α expression in the Jo-1 group was higher in comparison with the SRP, PM, DC, and HC groups. The expression of TREM-1 was observed in biopsied capillaries and the muscle membrane from patients with Jo-1 and in biopsied muscle fiber and capillaries from patients with DM and SRP. The depletion of Jo-1 antibodies by IgG of patients with Jo-1 antibody myositis reduced the Jo-1 antibody-induced complement-dependent cellular cytotoxicity in muscle endothelial cells.

DISCUSSION

Jo-1 antibodies from Jo-1 antibody myositis show complement-dependent cellular cytotoxicity in muscle endothelial cells. IgGs from patients with Jo-1, SRP, and DM increase the TREM-1 expression in endothelial cells and muscles.

An observational study of clinical recurrence in patients with interstitial lung disease related to the antisynthetase syndrome

OBJECTIVE

To describe the clinical characteristics and risk factors of clinical recurrence in interstitial lung disease related to antisynthetase syndrome (ARS-ILD).

METHODS

Patients diagnosed as ARS-ILD in Nanjing Drum Tower Hospital between January 2015 and November 2020 were retrospectively analyzed. Clinical information and treatment course were reviewed. The primary endpoint was the disease recurrence, and the secondary point was mortality. Univariate and multivariable Cox regression analyses were performed to identify risk factors for recurrence.

RESULTS

Totally, 132 patients with ARS-ILD received immunomodulation treatment from diagnosis. During follow-ups, sixty-nine patients showed recurrence, with a recurrency rate yielding 52.3%. The median duration from treatment initiation to recurrence was 11 (5-18) months. The median tapering course in the recurrence group was 8 (3-12.5) months, which was significantly shorter than the 16 (10-32) months in the no-recurrence group (p < 0.001). Fifty-eight patients experienced recurrence when the glucocorticoids (GC) dose dropped to 10 (9.375-15) mg/day. Twelve patients discontinued GC with a median treatment course of 11.5 (8-16.75) months, and 11 patients developed recurrence after discontinuing GC for 3 (1-4) months. Twelve patients died, with a mortality rate of 9.1%, and recurrence was not associated with increased mortality. The adjusted multivariate analysis showed that age, increased serum lactate dehydrogenase (LDH) level, relatively shorter tapering duration, and inappropriate GC discontinuation were associated with recurrence.

CONCLUSION

Recurrence of ARS-ILD was common during medication intensity reduction. Age, LDH, medication tapering duration, and discontinuation were risk factors for recurrence. Further efforts to reduce recurrence should take into consideration of these factors. Key Points • Recurrence is observed commonly with a recurrency rate 52.3% in patients with interstitial lung disease related to antisynthetase syndrome (ARS-ILD) when glucocorticoids (GC) tapering or discontinuation. • Age, increased serum lactate dehydrogenase (LDH) level, medication tapering duration, and GC discontinuation were identified to be significantly associated with the recurrence of ARS-ILD.

Successful treatment of rapid progressive interstitial lung disease in a case of anti-Zo antibody positive anti-synthetase syndrome

BACKGROUND

Anti-synthetase syndrome (ASS) is a chronic multisystemic autoimmune disease characterized by detectable anti-aminoacyl-transfer-RNA antibodies. Interstitial lung disease (ILD) in anti-synthetase syndrome patients is often severe and rapidly progressive. Anti-Zo (phenylalanyl) antibody is reported rarely in ASS. Therefore, the appropriate treatment of anti-Zo positive ASS is unclear.

CASE PRESENTATION

Here we present a case of anti-Zo-positive ASS with rapid progressive ILD (RP-ILD) in a Chinese patient successfully treated with a combination of systemic corticosteroids and tacrolimus.

CONCLUSION

We reviewed 13 anti-Zo-positive ASS patients (including our case) and summarized clinical features that have some differences with other ASS. Anti-Zo-positive ASS is a rare autoimmune disease with a high burden of ILD, is often severe and rapidly progressive. Corticosteroids with tacrolimus may improve patient outcomes in anti-Zo antibody positive ASS with RP-ILD.

Human epididymis protein 4 as a clinical biomarker in identifying interstitial lung disease in patients with idiopathic inflammatory myopathies

OBJECTIVE

Human epididymis protein 4 (HE4) can differentiate interstitial lung disease from patients with some rheumatic diseases. However, the clinical utility of HE4 in idiopathic inflammatory myopathies (IIM) remains unclear.

METHODS

80 IIM patients and 91 age and gender-matched healthy controls (HCs) were recruited. Clinical and laboratory data were recorded at baseline and 12 weeks. HE4 was tested by the method of electrochemical luminescence.

RESULTS

Compared to HCs, the levels of HE4 significantly elevated in IIM patients. Patients with elevated HE4 had a higher interstitial lung disease (ILD) prevalence. Among patients with ILD, histological patterns of organizing pneumonia had higher HE4 levels than non-specific interstitial pneumonia. Further, there was a positive correlation between HE4 and the semi-quantitative CT grade (r = 0.778, p < 0.001) and a negative relation between HE4 and the percentage of forced vital capacity (p < 0.001) and diffusing capacity of the lung for carbon monoxide (DLco) (p = 0.001). An optimal cut-off value of HE4 (79.6 pmol/L) for distinguishing IIM-ILD was analyzed by ROC analysis with an AUC of 0.733 (p = 0.002). Regression analysis revealed that elevated HE4 independently identified IIM-related ILD (OR 34.8, 95 %CI, 3.58-338.14, p = 0.002). With the improvement after treatment, serum HE4 levels were significantly decreased (p = 0.006), accompanied by improved DLco% (p = 0.012).

CONCLUSIONS

Serum HE4 was significantly elevated in patients with IIM and may be utilized as a serum biomarker to evaluate the disease severity and prognosis of IIM-related ILD.

Thigh MRI in antisynthetase syndrome, and comparisons with dermatomyositis and immune-mediated necrotizing myopathy

OBJECTIVES

To evaluate MRI changes to define muscle-lesion specific patterns in patients with antisynthetase syndrome (ASS), and compare them with those in other common idiopathic inflammatory myopathy subtypes.

METHODS

Qualitative and semi-quantitative thigh MRI evaluations were conducted in patients with ASS, DM and immune-mediated necrotizing myopathy (IMNM).

RESULTS

This study included 51 patients with ASS, 56 with DM and 61 with IMNM. Thigh MRI revealed muscle oedema (62.7%), myofascial oedema (90.2%), subcutaneous-tissue oedema (60.8%) and fatty infiltration of muscles (68.6%) in patients with ASS. Compared with IMNM, ASS and DM were associated with more frequent adductor-muscle relative sparing (40.6% vs 3.6%, P<0.001, and 25.6% vs 3.6%, P<0.001) and subcutaneous-tissue oedema (60.8% vs 23.0%, P<0.001, and 57.1% vs 23.0%, P<0.001). Although ASS and DM exhibited similar oedema patterns, there were certain subtle differences between them. The ASS group was less frequently symmetric (60.6% vs 88.4%, P=0.005, and 60.6% vs 80.0%, P=0.048), but more frequently showed myofascial oedema of the tensor fasciae latae (80.4% vs 48.2%, P<0.001, and 80.4% vs 31.1%, P<0.001) than either the DM or IMNM groups. The receiver operating characteristic curve analysis showed an optimal combination of thigh MRI findings had an area under the curve with 0.893 for diagnosing ASS.

CONCLUSION

Thigh MRI in ASS exhibited frequent myofascial oedema. ASS oedema patterns resembled those of DM more than those of IMNM. Bilateral asymmetry, adductor-muscle relative sparing and remarkable myofascial oedema of tensor fasciae latae were the most characteristic ASS imaging findings.

Anti-HMGCR myopathy overlaps with dermatomyositis-like rash: a distinct subtype of idiopathic inflammatory myopathy

OBJECTIVE

To characterize the clinical and pathological features of anti-HMGCR myopathy.

METHODS

The presence of anti-HMGCR antibody in the serum of 227 patients with idiopathic inflammatory myopathy (IIM) and 100 healthy control individuals was assessed by ELISA. All ELISA positive samples were retested by indirect immunofluorescence assay (IIFA) on HEK293 cells. The clinical findings, muscle pathological features, and treatment outcomes of patients with anti-HMGCR myopathy, along with comparisons between anti-HMGCR myopathy with and without dermatomyositis (DM)-like skin rashes, and among MSA-based subgroups were analyzed.

RESULTS

We established an optimized ELISA cutoff for anti-HMGCR antibody positivity as ≥ 5.28 U. The overall concordance between ELISA and IIFA was 96.83%. Twenty-one out of 227 IIM patients were anti-HMGCR-positive by both assays. Of these 21 patients, 9 had DM-like skin rashes, and 16 showed remarkable muscle inflammation; 5 patients were juvenile-onset, and 2 received statin treatment. The muscle biopsies from these patients demonstrated variable muscle necrosis and T cell infiltration. Most anti-HMGCR-positive patients achieved favorable outcomes following prednisone and additional immunotherapies. The anti-HMGCR myopathy patients with DM-like rashes, compared to those without DM-like rashes, were younger and had a shorter disease duration.

CONCLUSIONS

Optimization of cutoff of anti-HMGCR antibody assays with confirmation by alternative assays can result in higher sensitivity and specificity. DM-like skin rashes and lymphocytic infiltrates were not rare in patients with anti-HMGCR myopathy. These findings suggest that while anti-HMGCR myopathy may overlap with DM-like rash, it is pathologically different from classic DM, and should be considered a distinct subgroup of IIM.

Anti-Ku Antibody-Positive Myositis Presenting as a Wide Range of Axial Myopathies and Myocarditis: A Case Report and Review of the Literature

Idiopathic inflammatory myopathies (IIMs) are autoimmune diseases predominantly affecting proximal muscles; paraspinal muscle involvement is relatively rare. Because paraspinal myopathies do not always cause clinically-evident symptoms, the diagnosis of IIMs with axial myopathies can be challenging. Anti-Ku autoantibodies, initially reported in polymyositis/systemic sclerosis overlap syndrome, are myositis-associated antibodies (MAAs) observed in patients with a wide variety of connective tissue diseases (CTDs). Few reports have been published demonstrating predominant axial myopathy in IIM patients with anti-Ku antibodies. Herein, we investigated a previously healthy Japanese woman in her early 70s who presented with Raynaud's phenomenon, back pain, and exertional dyspnea. The creatine kinase (CK) was elevated and antinuclear antibody staining was positive, but myositis-specific antibodies (MSAs) were negative. Magnetic resonance imaging (MRI) revealed myocarditis and a wide range of axial muscle inflammation, including bilateral thoracolumbar paraspinal, infraspinatus, and trapezius muscles. The muscle biopsy was consistent with IIM. In addition, anti-Ku antibody was positive. Administration of prednisolone and tacrolimus quickly alleviated the symptoms and the CK level returned to normal. The diagnosis of IIM was arduous in this case because she did not present with camptocormia, muscle weakness involving the proximal limbs was not apparent, and MSAs were negative. Whether axial myopathy and myocarditis are more prevalent in IIM patients with than without anti-Ku antibodies is uncertain. Clinicians should suspect axial myopathy and MAAs, such as anti-Ku antibodies, especially in patients in whom muscle weakness of the proximal limbs is not noticeable.

Lymphocyte immunophenotyping in inflammatory myositis: a review

PURPOSE OF REVIEW

This is a comprehensive review of the current knowledge on predominant immune cell phenotypes involved in idiopathic inflammatory myopathies (IIM).

RECENT FINDINGS

Major circulating immune cell subpopulations described in IIM encompass the lymphocyte compartment. An unbalance in T cell subsets seems to consistently affect the peripheral and muscle compartment, with a predominance of CD4+ T and B cells in dermatomyositis, CD8+ T cells in polymyositis/inclusion body myositis (IBM) and novel findings highlighting novel proinflammatory T subsets, that is, CD8+Tbet+ and CD28- T cells across different IIM subsets. On the other hand, an impairment in Treg cells number and function has been described especially across polymyositis/dermatomyositis and IBM. Total T follicular helper (Tfh) cells, increased in immune-mediated necrotizing myopathy, skewed toward Tfh2 and Tfh17 in dermatomyositis, polymyositis, and juvenile dermatomyositis. B cell compartment is more rarely described in IIM, yet an unbalance in this pool is as well likely. Evidence of plasma cells increased in polymyositis, dermatomyositis, IBM, and Bregs decreased in dermatomyositis have been reported. Perturbations in the memory and naïve subsets are common in dermatomyositis/polymyositis and antisynthetase syndrome.

SUMMARY

Protean immune cell abnormalities characterize different IIM subsets, reflecting the complexity of these autoimmune conditions. A deeper understanding of B-cell and T-cell immunophenotyping may promote early diagnosis and identification of new potential therapeutic targets.

Antisynthetase Syndrome with Severe Interstitial Lung Disease in Pregnancy

Antisynthetase syndrome is a rare multisystem autoimmune disorder which clinically manifests with myositis, arthritis, interstitial lung disease, Raynaud phenomenon, and skin hyperkeratosis. Lung involvement represents the most severe form of disease and has rarely been reported in pregnancy. We present the case of a 22-year-old woman with antisynthetase syndrome and severe restrictive pulmonary disease who experienced a successful pregnancy and delivery. We discuss anesthetic considerations and highlight the importance of a multidisciplinary team approach in caring for parturients with multifactorial medical conditions.

The Association of Myositis Specific Antibodies in Patients with Inflammatory Myositis: Preliminary Data in Indian Patients

CONTEXT

Autoantibodies have a role in the diagnosis and prognosis in Autoimmune Inflammatory Myositis (AIM).

AIMS

The aim of this work was to study the prevalence and clinical correlation of myositis specific and associated antibodies (MSA and MAA) in AIM.

SETTING AND DESIGN

This was a cross-sectional observational study.

METHODS AND MATERIALS

Consecutive AIM patents were divided into groups as dermatomyositis (DM), polymyositis (PM), CTD-associated myositis (CTD-M), cancer-associated myositis (CAM) and juvenile myositis (JM). Their data along with serum samples were collected after obtaining informed consent. Sera was analyzed for IgG antibodies against Jo-1, PL-7, PL-12, EJ, SRP, Mi-2, MDA-5, TIF1γ, SAE1, SAE2, NXP2 and SSA/R052kD using the microELISA technique. The institutional ethics committee approved the study.

STATISTICAL ANALYSIS

SPSS software (version 24.0) was used. P value < 0.05 was considered statistically significant.

RESULTS

There were 48 patients (DM = 19, PM = 19, CTD-M = 5, CAM = 2, JM = 3) included. MSA were positive in 37.5% patients. Antibodies against Mi-2 were present in 6 (12.5%), Jo-1 in 5 (10.4%), 2 (4.1%) each had PL-7 and SRP antibodies. One patient (2%) each had MDA-5, NXP2 and TIf1g antibodies. Jo-1 antibody was associated with mechanic's hands and ILD. There was a significant association of rash in the Mi-2 group with none of the patients having ILD. Malignancy screening was negative in NXP2 and TIF1g antibody-positive patients. Ro52 was the most common MAA (33.3%) and was associated with mechanic's hand.

CONCLUSION

MSA was present in almost 40% of the cohort. Anti Jo-1 antibody was associated with mechanic's hands and ILD. None of the Mi-2 patients had ILD, which may point to a protective role of this antibody for ILD. The association of newer antibodies in Indian patients needs to be further studied in larger cohorts.

Cytokines and inflammatory mediators as promising markers of polymyositis/dermatomyositis

PURPOSE OF REVIEW

Idiopathic inflammatory myopathies (IIMs), known also as myositis, represent challenging group of heterogeneous muscle disorders characterized by symmetric proximal muscle weakness and evidence of muscle inflammation. The purpose of this review is to provide important updates on cytokines and inflammatory mediators related to myositis.

RECENT FINDINGS

In the past 5 years, multiple studies brought a fresh insight into the pathogenesis of myositis by introducing new factors or further characterizing the role of the well established mediators in myositis. Among the mediators reviewed in this article, special attention was paid to interferons, C-X-C motif chemokine ligand 10, interleukin-18 and the IL23/Th17 axis. Some of the recent work has also focused on the nontraditional cytokines, such as adipokines, myokines, S100 proteins, High Mobility Group Box 1 or B-cell activating factor and on several anti-inflammatory mediators. Moreover, microRNAs and their potential to reflect the disease activity or to regulate the inflammatory processes in myositis have recently been subject of intensive investigation. Some of the above-mentioned mediators have been proposed as promising clinical biomarkers or therapeutic targets for myositis.

SUMMARY

Several recent studies contributed to a better understanding of the pathogenesis of myositis and highlighted the clinical significance of certain inflammatory mediators. Application of these new findings may help to develop innovative approaches for patients' phenotyping, disease activity monitoring and potentially novel therapies.

Dermatomyositis autoantibodies: how can we maximize utility?

The past 15 years has seen significant advances in the characterization of myositis-specific autoantibodies (MSAs) and their associated phenotypes in patients with dermatomyositis (DM). As more careful studies are performed, it is clear that unique combinations of clinical and pathological phenotypes are associated with each MSA, despite the fact that there is considerable heterogeneity within antibody classes as well as overlap across the groups. Because risk for interstitial lung disease (ILD), internal malignancy, adverse disease trajectory, and, potentially response to therapy differ by DM MSA group, a deeper understanding of MSAs and validation and standardization of assays used for detection are critical for optimizing diagnosis and treatment. Like any test, the diagnostic sensitivity and specificity of assays for various MSAs is not perfect. Currently tests for MSAs are helpful at minimum for a clinician to assess relative risk or contribute to diagnosis and perhaps counsel the appropriate patient about what to expect. With international standardization and larger studies it is likely that more antibody tests will make their way into formal schemata for diagnosis and actionable risk assessment in DM. In this review, we summarize key considerations for interpreting the clinical and pathologic associations with MSA in DM and identify critical gaps in knowledge and practice that will maximize their clinical utility and utility for understanding disease pathogenesis.

Anti-MDA5 juvenile idiopathic inflammatory myopathy: a specific subgroup defined by differentially enhanced interferon-α signalling

OBJECTIVES

JDM and juvenile overlap myositis represent heterogeneous subtypes of juvenile idiopathic inflammatory myopathy (JIIM). Chronic evolution can occur in up to 60% of cases, and morbidity/mortality is substantial. We aimed to describe the clinical, biological, histological and type I IFN status in JIIM associated with anti-melanoma differentiation-associated protein 5 (anti-MDA5) autoantibodies at presentation (group 1) in comparison with other JIIM (group 2).

METHODS

This was a retrospective and prospective study of patients with JIIM ascertained from three French paediatric rheumatology reference centres between 2013 and 2019. Muscle biopsies were reviewed. Type I interferon pathway activity was assessed by dosage of IFNα serum protein and the expression of IFN-stimulated genes.

RESULTS

Sixty-four patients were included, 13 in group 1 (54% JDM and 46% juvenile overlap myositis) and 51 in group 2 (76% JDM and 24% juvenile overlap myositis). Group 1 patients demonstrated more arthritis, skin ulcerations, lupus features and interstitial lung disease, and a milder muscular involvement. Serum IFNα levels were higher in group 1 than 2, and decreased after treatment or improvement in both groups. Outcome was similar in both groups. Unconventional treatment (more than two lines) was required in order to achieve remission, especially when skin ulceration was reported.

CONCLUSION

This study indicates a higher frequency of arthritis, skin ulcerations and interstitial lung disease, but milder muscular involvement, in JIIM with positive anti-MDA5 autoantibodies compared with other JIIM. Our data support an important role of systemic IFNα in disease pathology, particularly in the anti-MDA5 auto-antibody-positive subgroup. In severe and refractory forms of JIIM, IFNα may represent a therapeutic target.

Interstitial lung disease in patients with antisynthetase syndrome: a retrospective case series study

PURPOSE

Antisynthetase syndrome (ASS) is a rare systemic autoimmune condition associated to the presence of anti-aminoacyl-tRNA synthetase antibodies. Interstitial lung disease (ILD) is the most prevalent manifestation of ASS and is a major determinant of morbidity and mortality. The aim of this study was to describe the radiological characteristics of patients with ASS-associated-ILD in our institution.

MATERIALS AND METHODS

Medical records from 2014 to 2020 were retrospectively reviewed and patients with a diagnosis of ASS and evidence of ILD on HRCT were included. HRCT images were reviewed by two thoracic radiologists in consensus. Five HRCT patterns were defined: cellular non-specific interstitial pneumonia (NSIP), organizing pneumonia (OP), mixed NSIP/OP pattern, acute interstitial pneumonia (AIP) pattern and fibrotic pattern. Descriptive statistics was calculated for all variables.

RESULTS

Twenty-two patients with ASS who met inclusion criteria were included. The disease presented with the typical triad of ASS in 45% of patients, 55% had ILD only at the onset. Cellular NSIP was present in 27% of patients, OP in 23%, mixed NSIP/OP in 9%, AIP in 18% and a fibrotic pattern in 23%.

CONCLUSION

HRCT findings in ASS-associated ILD are often non-specific; nevertheless, it is important to consider this diagnosis, especially in patients presenting with acute onset of symptoms.

Antisynthetase syndrome - much more than just a myopathy

The aim of the study was to summarize current knowledge on antisynthetase syndrome (ASS), including its epidemiology, pathogenesis, proposed so far diagnostic criteria, heterogeneity of clinical manifestations, prognostic factors and therapeutic possibilities. PubMed database was screened for "antisynthetase syndrome" OR "antisynthetase antibodies" between February and April 2020. Aminoacyl-tRNA synthetases participate in the immune system activation as antigens, but also serve chemoattractive and cytokine-resembling roles, initiating innate and adaptive pathways. Exposure to various inhaled antigens may induce the autoimmune cascade leading to ASS. NK cells with its impaired INF-y production as well as formation of NETs by neutrophils contribute to pathogenesis. The prevalence of symptoms vary significantly depending on the study with muscular, articular and pulmonary involvement being the most frequently observed. Although classified as subtype of idiopathic inflammatory myopathies, myositis may not necessarily be the prominent manifestation. Since clinical presentation is heterogeneous and symptoms can emerge gradually, ASS could be considered as a heterogeneous spectrum rather than a homogenous disease entity. The currently available classification criteria do not fully correspond with the clinical patterns of the disease. Therapy is based on glucocorticosteroids and other immunosuppressive agents. Randomized controlled trials, dedicated for patients with ASS, are needed to form treatment algorithms.

Die Diagnose liegt auf der Hand

Eine seltene Form der Dermatomyositis ist die klinische amyopathische Dermatomyositis (CADM). Charakterisiert ist sie durch das Fehlen einer bzw. durch eine nur sehr gering ausgeprägte Muskelbeteiligung. Dementsprechend sind die Kreatinkinase-Werte meist im Normalbereich. Typische Hautmanifestationen sind Gottron-Papeln und Mechanikerhände. Bei Nachweis eines MDa5 (Melanoma-differentiation-associated gene 5 intracellular pathogen sensor)-Antikörpers ist die CADM häufig mit einer rasch progredienten und schweren Verlaufsform einer interstitiellen Lungenerkrankung assoziiert. In der Lungenfunktion lässt sich eine Restriktion und eine Hypoxämie unterschiedlichen Ausmaßes nachweisen. Die HRCT-Bildgebung ist nicht spezifisch. Es lassen sich u. a. Milchglas, Retikulationen und Konsolidierungen beobachten. In der bronchioloalveolären Lavage zeigen sich gelegentlich vermehrt Lymphozyten. Histologisch ähnelt das Bild einer nicht-spezifischen interstitiellen Pneumonie oder einer organisierenden Pneumonie. Die Therapie richtet sich nach der Schwere der Ausprägung der klinischen Manifestation. Im Allgemeinen ist eine ausgeprägte immunsuppressive Therapie notwendig. Meist müssen verschiedene Immunsuppressiva kombiniert werden. Ein neuer Therapieansatz stellt die Verwendung des Januskinase-Inhibitors Tofacitinib dar. Zur Therapiekontrolle können der Ferritinspiegel und der MDa5-Antikörper-Titer verwendet werden. Es besteht eine hohe Mortalität von bis zu 84 %.

Functional Progression in Patients with Interstitial Lung Disease Resulted Positive to Antisynthetase Antibodies: A Multicenter, Retrospective Analysis

Antisynthetase syndrome (ASSD) is a rare autoimmune disease characterized by serologic positivity for antisynthetase antibodies. Anti-Jo1 is the most frequent, followed by anti PL-7, anti PL-12, anti EJ, and anti OJ antibodies. The lung is the most frequently affected organ, usually manifesting with an interstitial lung disease (ILD), which is considered the main determinant of prognosis. Some evidences suggest that non-anti-Jo-1 antibodies may be associated with more severe lung involvement and possibly with poorer outcomes, while other authors do not highlight differences between anti-Jo1 and other antisynthetase antibodies. In a multicenter, retrospective, “real life” study, we compared lung function tests (LFTs) progression in patients with ILD associated with anti-Jo1 and non-anti-Jo1 anti-synthetase antibodies to assess differences in lung function decline between these two groups. Therefore, we analyzed a population of 57 patients (56% anti-Jo1 positive), referred to the outpatient Clinic of four referral Centers in Italy (Modena, Monza, Siena, and Trieste) from 2008 to 2019, with a median follow-up of 36 months. At diagnosis, patients showed a mild ventilatory impairment and experienced an improvement of respiratory function during treatment. We did not observe statistically significant differences in LFTs at baseline or during follow-up between the two groups. Moreover, there were no differences in demographic data, respiratory symptoms onset (acute vs. chronic), extrapulmonary involvement, treatment (steroid and/or another immunosuppressant), or oxygen supplementation. Our study highlights the absence of differences in pulmonary functional progression between patients positive to anti-Jo-1 vs. non anti-Jo-1 antibodies, suggesting that the type of autoantibody detected in the framework of ASSD does not affect lung function decline.

Myositis-specific autoantibodies in adults with idiopathic inflammatory myopathy: correlations with diagnosis and disease activity

OBJECTIVE

To determine the relationship of myositis autoantibodies with the diagnosis and severity of idiopathic inflammatory myopathy (IIM) using the 2017 EULAR/ACR idiopathic inflammatory myopathy classification criteria and the myositis disease activity assessment tool (MDAAT).

METHODS

Patients who met the new diagnostic criteria were tested for serum myositis-specific autoantibodies (MSAs) and myositis-associated autoantibodies (MAAs), and then classified into different subgroups based on autoantibody positivity. Patients were also diagnosed with possible IIM, probable IIM, and definite IIM. The MDAAT was used to evaluate muscular and extramuscular disease activity. The relationships of diagnostic classification with positivity for different myositis autoantibodies were determined.

RESULTS

There were 118 patients, and 81% of them had one or more myositis autoantibody. Anti-Jo-1 was the most common MSA, and anti-Ro-52 was the most common MAA. Sixteen patients (14%) had possible IIM, 36 (31%) had probable IIM, and 66 (56%) had definite IIM. MSA-positive patients were significantly more common in the definite IIM group, but MAA positivity was unrelated to diagnostic classification. Positivity for MSAs or MAAs had no correlations with muscle disease activity. Extramuscular disease activity was greater in MSA-positive than MSA-negative patients, but MAA positivity had no significant association with extramuscular disease activity.

CONCLUSIONS

MSA positivity aids in the diagnosis of IIM. MSA positivity was associated with greater extramuscular disease activity. Improving the clinical application of MSAs may enhance the individualized treatment of patients with IMM. Key Points • In this paper, we explore the relationships between the myositis autoantibodies and the diagnosis and the disease activity of inflammatory myopathy. • Positive myositis-specific autoantibodies is associated with the establishment of diagnosis and higher extramuscular disease activity. • Thus, more extensive application of myositis autoantibodies maybe the key for further disease assessment and research.

Extended myositis-specific and -associated antibodies profile in systemic sclerosis: A cross-sectional study

OBJECTIVE

In systemic sclerosis (SSc) and idiopathic inflammatory myopathies (IIM), auto-antibodies are used in daily practice as potent biomarkers of clinical phenotypes. This study aimed at estimating the prevalence of myositis-specific (MSA) and myositis-associated (MAA) auto-antibodies in a well-characterised SSc patients cohort using two different immunoblot assays, and studying their clinical associations.

METHODS

In this cross-sectional study, the sera of 300 consecutive patients were tested at the same time with myositis antibodies Euroimmun® and D-tek® immunoblot assays.

RESULTS

Prevalence of MSA/MAA, MSA and MAA were 17.0%, 8.0% and 9.7%, respectively. When combining results of both tests, anti-PM/Scl 100 were found in 5.0% (95% confidence interval 2.8; 8.1); anti-PM/Scl 75 and anti-TIF1γ in 3.7% (1.8; 6.5); anti-Ku 3.0% (1.4; 5.6); anti-MDA5 in 1.3% (0.4; 3.4); anti-Mi-2 β, anti-NXP2, anti-PL-7 and anti-SRP in 0.7% (0.08; 2.4); anti-EJ and anti-PL-12 in 0.3% (0.01; 1.8) of patients. No reactivity against SAE1, Jo-1 or OJ was observed. Anti-PM/Scl 75 antibodies were associated with interstitial lung disease (80% vs. 42%) and myositis (27% vs. 3%); anti-Ku antibodies were associated with myositis (33% vs. 3%).

CONCLUSION

In this cross-sectional study of 300 SSc patients, the prevalence of MSA/MAA, MSA and MAA using immunoblot assays were 17.0%, 8.0% and 9.7%, respectively. MAA positivity was associated with ILD and myositis, but this study did not highlight any clinical associations with MSA positivity.

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.

Disease Specific Autoantibodies in Idiopathic Inflammatory Myopathies

Idiopathic inflammatory myopathies represent still a diagnostic and therapeutic challenge in different disciplines including neurology, rheumatology, and dermatology. In recent years, the spectrum of idiopathic inflammatory myopathies has been significantly extended and the different manifestations were described in more detail leading to new classification criteria. A major breakthrough has also occurred with respect to new biomarkers especially with the characterization of new autoantibody-antigen systems, which can be separated in myositis specific antibodies and myositis associated antibodies. These markers are detectable in approximately 80% of patients and facilitate not only the diagnostic procedures, but provide also important information on stratification of patients with respect to organ involvement, risk of cancer and overall prognosis of disease. Therefore, it is not only of importance to know the significance of these markers and to be familiar with the optimal diagnostic tests, but also with potential limitations in detection. This article focuses mainly on antibodies which are specific for myositis providing an overview on the targeted antigens, the available detection procedures and clinical association. As major tasks for the near future, the need of an international standardization is discussed for detection methods of autoantibodies in idiopathic inflammatory myopathies. Furthermore, additional investigations are required to improve stratification of patients with idiopathic inflammatory myopathies according to their antibody profile with respect to response to different treatment options.