Coexisting autoantibodies against transcription factor Sp4 are associated with decreased cancer risk in patients with dermatomyositis with anti-TIF1γ autoantibodies.

OBJECTIVES: In dermatomyositis (DM), autoantibodies are associated with unique clinical phenotypes. For example, anti-TIF1γ autoantibodies are associated with an increased risk of cancer. The purpose of this study was to discover novel DM autoantibodies. METHODS: Phage ImmunoPrecipitation Sequencing using sera from 43 patients with DM suggested that transcription factor Sp4 is a novel autoantigen; this was confirmed by showing that patient sera immunoprecipitated full-length Sp4 protein. Sera from 371 Johns Hopkins patients with myositis (255 with DM, 28 with antisynthetase syndrome, 40 with immune-mediated necrotising myopathy, 29 with inclusion body myositis and 19 with polymyositis), 80 rheumatological disease controls (25 with Sjogren's syndrome, 25 with systemic lupus erythematosus and 30 with rheumatoid arthritis (RA)) and 200 healthy comparators were screened for anti-SP4 autoantibodies by ELISA. A validation cohort of 46 anti-TIF1γ-positive patient sera from the University of Pittsburgh was also screened for anti-Sp4 autoantibodies. RESULTS: Anti-Sp4 autoantibodies were present in 27 (10.5%) patients with DM and 1 (3.3%) patient with RA but not in other clinical groups. In patients with DM, 96.3% of anti-Sp4 autoantibodies were detected in those with anti-TIF1γ autoantibodies. Among 26 TIF1γ-positive patients with anti-Sp4 autoantibodies, none (0%) had cancer. In contrast, among 35 TIF1γ-positive patients without anti-Sp4 autoantibodies, 5 (14%, p=0.04) had cancer. In the validation cohort, among 15 TIF1γ-positive patients with anti-Sp4 autoantibodies, 2 (13.3%) had cancer. By comparison, among 31 TIF1γ-positive patients without anti-Sp4 autoantibodies, 21 (67.7%, p<0.001) had cancer. CONCLUSIONS: Anti-Sp4 autoantibodies appear to identify a subgroup of anti-TIF1γ-positive DM patients with lower cancer risk.

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.

The indirect immunofluorescence assay autoantibody profiles of myositis patients without known myositis-specific autoantibodies.

OBJECTIVES: The indirect immunofluorescence assay (IIFA) is used to screen for the presence of autoantibodies. Our objective was to determine the prevalence and clinical features of IIFA positive myositis patients without known myositis-specific autoantibodies (MSA). METHODS: Sera from healthy comparators (HC) and patients with dermatomyositis (DM), inclusion body myositis (IBM), and polymyositis (PM) with no detectable MSA were tested by IIFA on HEp-2 cells. The pattern of positivity was classified according to the International Consensus on Antinuclear Antibody Patterns. The prevalence and frequency of each IIFA pattern were compared between the different groups. RESULTS: Sera from 100 HC, 71 DM, 53 IBM, and 69 PM subjects were included in the study. The IIFA was positive in 35% HC compared to 66% DM (p<0.001), 49% IBM, and 64% (p<0.001) PM sera. Among IIFA positive sera, the staining was moderate or intense in 43% HC compared to 79% DM (p<0.001) but just 54% IBM, and 52% PM sera. IIFA positivity was predominantly nuclear in all groups (all >69%). The most common pattern in myositis patients was fine speckled with no differences between groups. In general, IIFA positive and negative DM patients showed similar clinical features and disease activity. CONCLUSIONS: Half of MSA-negative DM patients have moderate/strong IIFA positivity, predominantly with a fine speckled pattern. In contrast, MSA-negative PM, IBM, and healthy comparators are more often weakly positive for IIFA. These findings suggest that unidentified autoantibodies are more likely to exist in DM patients than in the other myositis groups.

Efficacy of plasma exchange in anti-MDA5-positive dermatomyositis with interstitial lung disease under combined immunosuppressive treatment.

OBJECTIVES: Rapidly progressive interstitial lung disease (RP-ILD) with poor prognosis often accompanies anti-melanoma differentiation-associated gene 5 (MDA5)-positive DM. Combined immunosuppressive therapy, including glucocorticoids, calcineurin inhibitors and intravenous cyclophosphamide (IVCY) is reportedly effective in DM with RP-ILD, but some patients remain resistant to therapy. We examined the utility of plasma exchange (PE) in such intractable cases and investigated the prognostic factors of the disease. METHODS: Thirty-eight anti-MDA5-positive DM-ILD patients who received the combined immunosuppressive therapy were retrospectively reviewed. Their serum cytokines were evaluated by multiplex assay before treatment. The patients were divided into two groups: those who achieved remission without exacerbation of respiratory dysfunction (n = 25, group A) and those who progressed to hypoxemia during the treatment (n = 13, group B). RESULTS: PE was carried out in eight group B patients, but none of group A. Five of the eight treated with PE survived, while the five untreated patients died (P =0.04). Higher neutrophil lymphocyte ratio, higher serum ferritin, hypoxemia, high-resolution computed tomography (HRCT) score before treatment and increase of Krebs von Lungen-6 (KL-6) in the first 4 weeks of the treatment were the prognostic factors for disease progression. Serum cytokines such as IL-1, IL-6, IL-8, IL-10, IL-12p70, IL-18 and sCD163 levels were higher in group B than group A. CONCLUSION: PE should be an effective adjuvant treatment in anti-MDA5-positive DM with RP-ILD. Assessment of basal laboratory tests or monocyte/macrophage-derived cytokines and the increase of KL-6, HRCT score and hypoxemia may help us to predict intractable cases and to make early treatment decisions regarding PE in anti-MDA5-positive DM.

Serum matrix metalloproteinase levels in polymyositis/dermatomyositis patients with interstitial lung disease.

OBJECTIVE: We aimed to clarify the clinical significance of serum levels of MMPs in interstitial lung disease (ILD) complicated with PM/DM (PM/DM-ILD). METHODS: We retrospectively analysed serum levels of seven subsets of MMPs in 52 PM/DM-ILD patients diagnosed at Kyoto University Hospital or Tenri Hospital from January 2005 to December 2014. The patients were sub-grouped based on the presence of anti-amimoacyl-tRNA synthetase antibody (anti-ARS antibody), anti-melanoma differentiation-associated protein 5 antibody (anti-MDA5 antibody) or lack of the antibodies (ARS-ILD, MDA5-ILD and other-ILD groups, respectively) and independently analysed. Eighteen PM/DM patients without ILD and 55 healthy control were also analysed. Associations between serum levels of MMPs and clinical findings including mortality were analysed. RESULTS: Among the MMPs analysed, MMP-7 serum levels in the ARS-ILD group were significantly higher compared with those in any of the other groups of PM/DM patients or in healthy controls. On the other hand, in the MDA5-ILD group, serum MMP-7 levels >5.08 ng/ml were associated with worse overall survival both in univariate (P = 0.017; odds ratio 18.0; 95% CI 1.69, 192.00) and multivariate (P = 0.027; odds ratio 14.60; 95% CI 1.11, 192.00) analyses. Immunohistochemical analysis suggested that MMP-7 was expressed in type II alveolar epithelial cells adjacent to the fibrotic lesions. CONCLUSION: Serum MMP-7 levels were higher in anti-ARS antibody-positive PM/DM-ILD patients, while higher serum MMP-7 levels among anti-MDA5 antibody-positive PM/DM-ILD patients were associated with a worse prognosis. Fibrotic processes may be associated with the elevation of serum MMP-7 levels.

Serum neopterin as well as ferritin, soluble interleukin-2 receptor, KL-6 and anti-MDA5 antibody titer provide markers of the response to therapy in patients with interstitial lung disease complicating anti-MDA5 antibody-positive dermatomyositis.

Objective: This study identified biomarkers that can be used to assess disease activity and response to therapy in patients with interstitial lung disease complicating anti-melanoma differentiation-associated gene 5 (MDA5) antibody (Ab)-positive clinically amyopathic dermatomyositis (CADM). Methods: In 15 patients with interstitial lung disease complicating anti-MDA5 Ab-positive CADM, anti-MDA5 Ab, neopterin, interleukin (IL)-18, ferritin, and soluble interleukin 2 receptor (sIL-2R) levels were measured in cryopreserved serum specimens before and at multiple times after remission induction therapy, and their correlations were assessed. Results: Anti-MDA5 Ab, neopterin, IL-18, ferritin, and sIL-2R levels did not differ significantly between patients who survived and those who succumbed to the disease. In many cases, serum anti-MDA5 Ab titers were over the upper limit (over 150 index value) before treatment in the usual measuring method, and gradually decreased to the normal range at stable phase. Meanwhile, serum neopterin levels (21.6 [15.3-48.3] nmol/L) were significantly elevated in newly diagnosed patients and fell to 6.8 (5-11.4) nmol/L at 6 months after treatment introduction. Conclusions: Elevated serum neopterin as well as ferritin, sIL-2R, KL-6, and anti-MDA5 Ab titer might help identify patients with interstitial lung disease complicated with DM and might be useful in monitoring response to therapy.

Splicing variant of WDFY4 augments MDA5 signalling and the risk of clinically amyopathic dermatomyositis.

OBJECTIVES: Idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of rare autoimmune diseases in which both genetic and environmental factors play important roles. To identify genetic factors of IIM including polymyositis, dermatomyositis (DM) and clinically amyopathic DM (CADM), we performed the first genome-wide association study for IIM in an Asian population. METHODS: We genotyped and tested 496 819 single nucleotide polymorphism for association using 576 patients with IIM and 6270 control subjects. We also examined the causal mechanism of disease-associated variants by in silico analyses using publicly available data sets as well as by in in vitro analyses using reporter assays and apoptosis assays. RESULTS: We identified a variant in WDFY4 that was significantly associated with CADM (rs7919656; OR=3.87; P=1.5×10-8). This variant had a cis-splicing quantitative trait locus (QTL) effect for a truncated WDFY4isoform (tr-WDFY4), with higher expression in the risk allele. Transexpression QTL analysis of this variant showed a positive correlation with the expression of NF-κB associated genes. Furthermore, we demonstrated that both WDFY4 and tr-WDFY4 interacted with pattern recognition receptors such as TLR3, TLR4, TLR9 and MDA5 and augmented the NF-κB activation by these receptors. WDFY4 isoforms also enhanced MDA5-induced apoptosis to a greater extent in the tr-WDFY4-transfected cells. CONCLUSIONS: As CADM is characterised by the appearance of anti-MDA5 autoantibodies and severe lung inflammation, the WDFY4 variant may play a critical role in the pathogenesis of CADM.

Splicing factor proline/glutamine-rich is a novel autoantigen of dermatomyositis and associated with anti-melanoma differentiation-associated gene 5 antibody.

OBJECTIVE: Anti-MDA5 antibody positive dermatomyositis (DM) and clinically amyopathic DM (CADM) often develop into rapidly progressive interstitial lung disease, but their pathogenesis remains unclear. We observed that sera from DM/CADM patients immunoprecipitated a common 110 kDa polypeptide. We investigated this autoantigen and its clinical significance. METHODS: Autoantibodies were screened in 333 patients with various connective tissue diseases (CTDs) and 20 healthy controls (HCs) by immunoprecipitation with [35S]methionine-labeled HeLa cells. Immunoabsorbent column chromatography was used to purify the reactive autoantigen which was subsequently analyzed by peptide mass fingerprinting. RESULTS: Anti-110 kDa antibody was detected in sera from 27 DM/CADM patients, but not in sera from other CTD patients or HCs. All patients with anti-110 kDa antibody had anti-MDA5 antibody. The maximum KL-6 levels in anti-110 kDa antibody-positive patients were higher than in anti-110 kDa antibody-negative patients, and all anti-MDA5-antibody-positive patients who showed the recurrence of DM/CADM were anti-110 kDa antibody-positive. The corresponding autoantigen was identified as splicing factor proline/glutamine-rich protein (SFPQ). In some cases, anti-SFPQ antibody was detected at diagnosis (early-detected group), but in other cases, it appeared during the disease course (delayed-detected group). The diagnosis timing of DM/CADM showed seasonal patterns according to the timing of anti-SFPQ antibody appearance. Specifically, 77% (10/13) of patients were diagnosed between August and October in the early-detected group, while 57% (8/14) of patients were diagnosed between January and March in the delayed-detected group. CONCLUSIONS: Some anti-MDA5 antibody-positive patients had an antibody to SFPQ, which is known to play a role in innate immune responses. Anti-SFPQ antibody may be involved in the chronic disease course of DM/CADM. The diagnosis timing of DM/CADM in anti-MDA5 antibody-positive patients showed seasonal patterns according to the timing of anti-SFPQ antibody appearance. These findings may provide new insights into the pathogenesis of DM/CADM.

Juvenile polymyositis associated with anti-OJ (anti-isoleucyl-tRNA synthetase) autoantibody in a 13-year-old girl.

A 13-year-old girl was admitted for persistent thigh pain and remittent fever and was diagnosed as having juvenile polymyositis. Although the initial treatment with 2 cycles of methylprednisolone pulse therapy failed to achieve full remission, the second-line treatment with intravenous cyclophosphamide pulse therapy was effective. Anti-OJ antibody, which is one of anti-aminoacyl-tRNA synthetase (ARS) antibodies and is rare in adult polymyositis, was detected. Assessment of anti-ARS autoantibodies may facilitate diagnosis and management of juvenile polymyositis.

Proteomic identification of heterogeneous nuclear ribonucleoprotein K as a novel cold-associated autoantigen in patients with secondary Raynaud's phenomenon.

OBJECTIVE: The aim of this study was to identify cold-associated autoantibodies in patients with RP secondary to CTDs. METHODS: Indirect immunofluorescence staining was performed on non-permeabilized cold-stimulated normal human dermal microvascular endothelial cells (dHMVECs), using patients' sera. Cold-induced alterations in cell surface proteomes were analysed by isobaric tag for relative and absolute quantitation (iTRAQ) analysis. Serological proteome analysis (SERPA) was applied to screen cold-associated autoantigens. The prevalence of the candidate autoantibody was determined by ELISA in 290 patients with RP secondary to CTDs (SSc, SLE or MCTD), 10 patients with primary RP and 27 healthy controls. RESULTS: Enhanced cell surface immunoreactivity was detected in cold-stimulated dHMVECs when incubated with sera from patients with secondary RP. By iTRAQ analysis, many proteins, including heterogeneous nuclear ribonucleoprotein K (hnRNP-K), were found to be increased on the cell surface of dHMVECs after cold stimulation. By the SERPA approach, hnRNP-K was identified as a candidate autoantigen in patients with secondary RP. Cold-induced translocation of hnRNP-K to the cell surface was confirmed by immunoblotting and flow cytometry. By ELISA analysis, patients with secondary RP show a significantly higher prevalence of anti-hnRNP-K autoantibody (30.0%, 61/203) than patients without RP (9.2%, 8/87, P = 0.0001), patients with primary RP (0%, 0/10, P = 0.0314) or healthy controls (0%, 0/27, P = 0.0001). CONCLUSION: By comprehensive proteomics, we identified hnRNP-K as a novel cold-associated autoantigen in patients with secondary RP. Anti-hnRNP-K autoantibody may potentially serve as a biomarker for RP secondary to various CTDs.

Screening for IgG4-type anti-nuclear antibodies in IgG4-related disease.

BACKGROUND: Immunoglobulin (Ig) G4-related disease (IgG4-RD) is characterized by elevated serum IgG4 and infiltration of IgG4(+) plasma cells into multiple organs. It is not known whether serum IgG4 is autoreactive in IgG4-RD. METHODS: We measured anti-nuclear antibody (ANA) in 19 IgG4-RD cases, determined IgG subclasses of the ANA, and compared them with those of other systemic autoimmune diseases (systemic lupus erythematosus, Sjögren's syndrome, systemic sclerosis, and polymyositis), using subclass-based ANA test (indirect immunofluorescence). RESULTS: 58 % of IgG4-RD cases were ANA-positive (cut-off: 1:40). Whereas their subclass of ANA was predominantly IgG2, we observed no IgG4-type ANA. In systemic autoimmune diseases, subclasses of ANA were mostly IgG1, 2, or 3, but IgG4-type ANA was very rarely detected. We also found several patients in whose serum ANA patterns differed among IgG subclasses, probably due to the difference of corresponding autoantigens. CONCLUSIONS: Although IgG4 is highly elevated in sera of IgG4-RD patients, their ANA do not include IgG4 subclass. These results offer new insight into the role of IgG4 and the pathogenesis of IgG4-RD, implying that each IgG subclass tends to cover its own spectrum of antigens, and IgG4 is not preferentially used to make ANA.

Early Initiation of Plasma Exchange Therapy for Anti-MDA5+Dermatomyositis with Refractory Rapidly Progressive Interstitial Lung Disease.

Objectives Dermatomyositis (DM) is often associated with fatal anti-melanoma differentiation-associated gene 5 (MDA5) antibody-positive rapidly progressive interstitial lung disease (RP-ILD). RP-ILD often fails to respond to intensive treatment and has a poor prognosis. We examined the effectiveness of early plasma exchange therapy plus intensive treatment with high-dose corticosteroids and multiple immunosuppressants. Methods Autoantibodies were identified by an immunoprecipitation assay and enzyme-linked immunosorbent assay. All clinical and immunological data were collected retrospectively from medical charts. We divided patients into two groups based on treatment regimen: intensive immunosuppressive therapy alone as initial treatment (IS group) and early initiation of plasma exchange (PE) plus intensive immunosuppressive therapy (ePE group). Early PE therapy was designated if PE therapy was initiated within two weeks of starting treatment. Comparisons of the treatment response and prognosis between groups were performed. Patients Anti-MDA5-positive DM with RP-ILD was screened. Results Forty-four RP-ILD and DM patients had anti-MDA5 antibodies. Four patients were excluded because they died before receiving sufficient combined immunosuppressive therapy or before the evaluation of the immunosuppressive treatment effectiveness (IS, n=31; ePE, n=9). All 9 patients in the ePE group had improved respiratory symptoms and were alive, whereas 12 of 31 patients in the IS group died (100 vs. 61%, p=0.037). Of the 8 patients who had 2 values for a poor prognosis, indicating the highest risk for death using the MCK model, 3 of 3 patients in the ePE group and 2 of 5 in the IS group were alive (100 vs. 40%, p=0.20). Conclusion The early initiation of ePE therapy plus intensive immunosuppressive therapy was effective for patients with DM and refractory RP-ILD.

Interstitial lung disease in myositis: clinical subsets, biomarkers, and treatment.

Interstitial lung disease (ILD) is the most frequent organ involvement (found in nearly half) of myositis patients, but it reveals various clinical courses and therapeutic responsiveness according to clinical and serological subsets. Autoantibodies, as well as imaging and histopathological studies, are useful for the classification of ILD in myositis and provide useful information for predicting prognosis and determining treatment. Antisynthetase antibodies are correlated with chronic and recurrent ILD, whereas anti-CADM-140 (MDA5/IFIH1) antibodies are a marker of acute progressive ILD in clinically amyopathic dermatomyositis. Serum KL-6, SP-D, and ferritin are useful biomarkers for monitoring the activity and severity of ILD. Regarding treatment, glucocorticoids are the first-line drug, but additional immunomodulating drugs are also used in refractory patients. Cyclophosphamide and calcineurin inhibitors (cyclosporine and tacrolimus) appear to be the key drugs in the treatment of refractory myositis-ILD. Rituximab may become another candidate if these drugs are not effective.

Early initiation of plasma exchange therapy for a patient with anti-MDA5 autoantibody-positive dermatomyositis developing rapidly progressive interstitial lung disease.

Dermatomyositis (DM) is a categorised as one of idiopathic inflammatory myopathy (IIM) indicated by symmetrical proximal muscle weakness as well as characteristic cutaneous manifestations typical of DM. Clinically amyopathic dermatomyositis (CADM), a subtype of DM, shows only the skin involvement without any clinical signs of myositis. This condition is often associated with fatal anti-MDA5 antibody-positive rapidly progressive interstitial lung disease (RP-ILD), especially in Eastern Asian populations. Here, we report a CADM patient with anti-MDA5 antibody-positive RP-ILD whom we successfully treated by early initiation of plasma exchange (PE) together with multiple immunosuppressive therapies. In this patient, initial treatment with high-dose prednisolone (PSL), tacrolimus and intermittent intravenous cyclophosphamide had resulted in no obvious improvement in the respiratory condition. Therefore, soon after the first evaluation, we initiated PE therapy in addition to these multiple immunosuppressive therapies. Although the patient had pneumomediastinum, cytomegalovirus and fungal infections over the clinical course, RP-ILD did gradually improved and the anti-MDA5 titre decreased down to within the normal range paralleled by improvement in the patient's respiratory condition.

Multicenter Prospective Study of the Efficacy and Safety of Combined Immunosuppressive Therapy With High-Dose Glucocorticoid, Tacrolimus, and Cyclophosphamide in Interstitial Lung Diseases Accompanied by Anti-Melanoma Differentiation-Associated Gene 5-Positive Dermatomyositis.

OBJECTIVE: Interstitial lung disease (ILD) accompanied by anti-melanoma differentiation-associated gene 5 (anti-MDA-5)-positive dermatomyositis (DM) is often rapidly progressive and associated with poor prognosis. Because there is no established treatment, we undertook this study to prospectively evaluate the efficacy and safety of a combined immunosuppressive regimen for anti-MDA-5-positive DM patients with ILD. METHODS: Adult Japanese patients with new-onset anti-MDA-5-positive DM with ILD (n = 29) were enrolled at multiple study centers from 2014 to 2017. They were treated with a regimen of high-dose glucocorticoids (GCs), tacrolimus, and intravenous cyclophosphamide (IV CYC). Plasmapheresis was used if a patient's condition worsened after the regimen started. The primary end point was 6-month survival, which was compared between this group of patients and a historical control group (n = 15) consisting of anti-MDA-5-positive DM patients with ILD who received step-up treatment (high-dose GC and stepwise addition of immunosuppressant). Secondary end points were 12-month survival rate, adverse events, and changes in laboratory data. RESULTS: The combined immunosuppressive regimen group showed significantly higher 6-month survival rates than the step-up treatment group (89% versus 33%; P < 0.0001). Over a period of 52 weeks, improvements in anti-MDA-5 titers, serum ferritin levels, vital capacity, and chest high-resolution computed tomography scores were observed. The combined immunosuppressive regimen group received IV CYC nearly 20 days earlier with shorter intervals and tended to receive plasmapheresis more often than patients undergoing step-up treatment. Cytomegalovirus reactivation was frequently observed over 52 weeks. CONCLUSION: A combined immunosuppressive regimen is effective for anti-MDA-5-positive DM patients with ILD. Plasmapheresis can be used for additional effect in intractable disease. Patients should be carefully monitored for opportunistic infections during treatment.

Neutrophil dysregulation is pathogenic in idiopathic inflammatory myopathies.

Idiopathic inflammatory myopathies (IIM) are characterized by muscle inflammation and weakness, myositis-specific autoantibodies (MSAs), and extramuscular organ damage. The role of neutrophil dysregulation and neutrophil extracellular traps (NETs) in IIM is unclear. We assessed whether pathogenic neutrophil subsets (low-density granulocytes [LDGs]) and NETs were elevated in IIM, associated with clinical presentation and MSAs, and their effect on skeletal myoblasts and myotubes. Circulating NETs and LDGs were quantified and correlated with clinical measures. Specific MSAs were tested for their ability to induce NETs. NETs and neutrophil gene expression were measured in IIM biopsies. Whether NETs damage skeletal myoblasts and myotubes was tested. Circulating LDGs and NETs were increased in IIM. IIM LDGs had an enhanced ability to form NETs. LDGs and NETs correlated with IIM disease activity and muscle damage. The serum MSA anti-MDA5 correlated with circulating and tissue NETs and directly enhanced NET formation. An enhanced neutrophil gene signature was present in IIM muscle and associated with muscle injury and tissue IFN gene signatures. IIM NETs decreased the viability of myotubes in a citrullinated histone-dependent manner. Dysregulated neutrophil pathways may play pathogenic roles in IIM through their ability to directly injure muscle cells and other affected tissues.

More prominent muscle involvement in patients with dermatomyositis with anti-Mi2 autoantibodies.

OBJECTIVE: To define the clinical phenotype of dermatomyositis (DM) with anti-Mi2 autoantibodies. METHODS: In this longitudinal cohort study, the prevalence and severity of clinical features at disease onset and during follow-up in patients with anti-Mi2-positive DM were compared to patients with anti-Mi2-negative DM, antisynthetase syndrome (AS), and immune-mediated necrotizing myopathy (IMNM). Longitudinal anti-Mi2 autoantibody titers were assessed. RESULTS: A total of 58 patients with anti-Mi2-positive DM, 143 patients with anti-Mi2-negative DM, 162 patients with AS, and 170 patients with IMNM were included. Among patients with anti-Mi2-positive DM, muscle weakness was present in 60% at disease onset and occurred in 98% during longitudinal follow-up; fewer patients with anti-Mi2-negative DM developed weakness (85%; p = 0.008). Patients with anti-Mi2-positive DM were weaker and had higher creatine kinase (CK) levels than patients with anti-Mi2-negative DM or patients with AS. Muscle biopsies from patients with anti-Mi2-positive DM had prominent necrosis. Anti-Mi2 autoantibody levels correlated with CK levels and strength (p < 0.001). With treatment, most patients with anti-Mi2-positive DM had improved strength and CK levels; among 10 with multiple serum samples collected over 4 or more years, anti-Mi2 autoantibody titers declined in all and normalized in 3, 2 of whom stopped immunosuppressant treatment and never relapsed. Patients with anti-Mi2-positive DM had less calcinosis (9% vs 28%; p = 0.003), interstitial lung disease (5% vs 16%; p = 0.04), and fever (7% vs 21%; p = 0.02) than did patients with anti-Mi2-negative DM. CONCLUSIONS: Patients with anti-Mi2-positive DM have more severe muscle disease than patients with anti-Mi2-negative DM or patients with AS. Anti-Mi2 autoantibody levels correlate with disease severity and may normalize in patients who enter remission.