Phage display of environmental protein toxins and virulence factors reveals the prevalence, persistence, and genetics of antibody responses.

Microbial exposures are crucial environmental factors that impact healthspan by sculpting the immune system and microbiota. Antibody profiling via Phage ImmunoPrecipitation Sequencing (PhIP-Seq) provides a high-throughput, cost-effective approach for detecting exposure and response to microbial protein products. We designed and constructed a library of 95,601 56-amino acid peptide tiles spanning 14,430 proteins with "toxin" or "virulence factor" keyword annotations. We used PhIP-Seq to profile the antibodies of ∼1,000 individuals against this "ToxScan" library. In addition to enumerating immunodominant antibody epitopes, we studied the age-dependent stability of the ToxScan profile and used a genome-wide association study to find that the MHC-II locus modulates bacterial epitope selection. We detected previously described anti-flagellin antibody responses in a Crohn's disease cohort and identified an association between anti-flagellin antibodies and juvenile dermatomyositis. PhIP-Seq with the ToxScan library is thus an effective tool for studying the environmental determinants of health and disease at cohort scale.

Association with HLA-DRß1 position 37 distinguishes juvenile dermatomyositis from adult-onset myositis.

Juvenile dermatomyositis (JDM) is a rare, severe autoimmune disease and the most common idiopathic inflammatory myopathy of children. JDM and adult-onset dermatomyositis (DM) have similar clinical, biological and serological features, although these features differ in prevalence between childhood-onset and adult-onset disease, suggesting that age of disease onset may influence pathogenesis. Therefore, a JDM-focused genetic analysis was performed using the largest collection of JDM samples to date. Caucasian JDM samples (n = 952) obtained via international collaboration were genotyped using the Illumina HumanCoreExome chip. Additional non-assayed human leukocyte antigen (HLA) loci and genome-wide single-nucleotide polymorphisms (SNPs) were imputed. HLA-DRB1*03:01 was confirmed as the classical HLA allele most strongly associated with JDM [odds ratio (OR) 1.66; 95% confidence interval (CI) 1.46, 1.89; P = 1.4 × 10-14], with an independent association at HLA-C*02:02 (OR = 1.74; 95% CI 1.42, 2.13, P = 7.13 × 10-8). Analyses of amino acid positions within HLA-DRB1 indicated that the strongest association was at position 37 (omnibus P = 3.3 × 10-19), with suggestive evidence this association was independent of position 74 (omnibus P = 5.1 × 10-5), the position most strongly associated with adult-onset DM. Conditional analyses also suggested that the association at position 37 of HLA-DRB1 was independent of some alleles of the Caucasian HLA 8.1 ancestral haplotype (AH8.1) such as HLA-DQB1*02:01 (OR = 1.62; 95% CI 1.36, 1.93; P = 8.70 × 10-8), but not HLA-DRB1*03:01 (OR = 1.49; 95% CR 1.24, 1.80; P = 2.24 × 10-5). No associations outside the HLA region were identified. Our findings confirm previous associations with AH8.1 and HLA-DRB1*03:01, HLA-C*02:02 and identify a novel association with amino acid position 37 within HLA-DRB1, which may distinguish JDM from adult DM.

Development of a computed tomography calcium scoring technique for assessing calcinosis distribution, pattern and burden in dermatomyositis.

OBJECTIVES: To utilize whole-body CT imaging and calcium scoring techniques as tools for calcinosis assessment in a prospective cohort of patients with adult and juvenile dermatomyositis (DM and JDM, respectively). METHODS: Thirty-one patients (14 DM and 17 JDM) who fulfilled Bohan and Peter Classification criteria as probable or definite DM, the EULAR-ACR criteria for definite DM, and with calcinosis identified by physical examination or prior imaging studies were included. Non-contrast whole-body CT scans were obtained using low-dose radiation procedures. Scans were read qualitatively and quantitated. We calculated the sensitivity and specificity of calcinosis detection of physician physical exam against CT. We quantified calcinosis burden using the Agatston scoring technique. RESULTS: We identified five distinct calcinosis patterns: Clustered, Disjoint, Interfascial, Confluent and Fluid-filled. Novel locations of calcinosis were observed, including the cardiac tissue, pelvic and shoulder bursa, and the spermatic cord. Quantitative measures using Agatston scoring for calcinosis were used in regional distributions across the body. Physician physical exams had a sensitivity of 59% and a specificity of 90% compared with CT detection. A higher calcium score correlated with higher Physician Global Damage, Calcinosis Severity scores, and disease duration. CONCLUSION: Whole-body CT scans and the Agatston scoring metric define distinct calcinosis patterns and provide novel insights relating to calcinosis in DM and JDM patients. Physicians' physical examinations underrepresented the presence of calcium. Calcium scoring of CT scans correlated with clinical measures, which suggests that this method may be used to assess calcinosis and follow its progression.

Performance of the 2017 EULAR/ACR Classification Criteria for adult and juvenile idiopathic inflammatory myopathies and their major subgroups: a scoping review.

The 2017 EULAR/ACR classification criteria for adult/juvenile idiopathic inflammatory myopathies (IIM) were established using a data-driven approach by an international group of myositis experts to allow classification of IIM and its major subtypes. Since their publication, the performance of the criteria has been tested in multiple cohorts worldwide and significant limitations have been identified. Moreover, the understanding and classification of IIM have evolved since 2017. This scoping review was undertaken as part of a large international project to revise the EULAR/ACR criteria and aims to i) summarise the evidence from the current literature on the performance characteristics of the 2017 EULAR/ACR classification criteria in various cohorts and IIM subtypes, and ii) delineate the factors that need to be considered in the revision of the classification criteria. A systematic search of Medline (via PubMed), Cumulative Index to Nursing and Allied Health Literature, and conference abstract archives was conducted independently by three investigators for studies on the EULAR/ACR criteria published between October 2017 and January 2023. This scoping review of 19 articles and 13 abstracts revealed overall good performance characteristics of the EULAR/ACR criteria for IIM, yet deficiencies in lack of inclusion of certain IIM subtypes, such as immune mediated necrotising myopathy, amyopathic dermatomyositis, antisynthetase syndrome and overlap myositis. Published modifications that may improve the performance characteristics of the criteria for classification of IIM subtypes were also summarised. The results of this review suggest that a revision of the EULAR/ACR criteria is warranted.

A protocol for scoping reviews on the role of whole-body and dedicated body-part magnetic resonance imaging for assessment of adult and juvenile idiopathic inflammatory myopathies.

Currently, standardized magnetic resonance imaging (MRI) scoring systems and protocols for assessment of idiopathic inflammatory myopathies (IIMs) in children and adults are lacking. Therefore, we will perform a scoping review of the literature to collate and evaluate the existing semi-quantitative and quantitative MRI scoring systems and protocols for the assessment and monitoring of skeletal muscle involvement in patients with IIMs. The aim is to compile evidence-based information that will facilitate the future development of a universal standardized MRI scoring system for both research and clinical applications in IIM. A systematic search of electronic databases (PubMed, EMBASE, and Cochrane) will be undertaken to identify relevant articles published between January 2000 and October 2023. Data will be synthesized narratively. This scoping review seeks to comprehensively summarize and evaluate the evidence on the scanning protocols and scoring systems used in the assessment of diagnosis, disease activity, and damage using skeletal muscle MRI in IIMs. The results will allow the development of consensus recommendations for clinical practice and enable the standardization of research methods for the MRI assessment of skeletal muscle changes in patients with IIMs.

Low copy numbers of complement C4 and C4A deficiency are risk factors for myositis, its subgroups and autoantibodies.

BACKGROUND: Idiopathic inflammatory myopathies (IIM) are a group of autoimmune diseases characterised by myositis-related autoantibodies plus infiltration of leucocytes into muscles and/or the skin, leading to the destruction of blood vessels and muscle fibres, chronic weakness and fatigue. While complement-mediated destruction of capillary endothelia is implicated in paediatric and adult dermatomyositis, the complex diversity of complement C4 in IIM pathology was unknown. METHODS: We elucidated the gene copy number (GCN) variations of total C4, C4A and C4B, long and short genes in 1644 Caucasian patients with IIM, plus 3526 matched healthy controls using real-time PCR or Southern blot analyses. Plasma complement levels were determined by single radial immunodiffusion. RESULTS: The large study populations helped establish the distribution patterns of various C4 GCN groups. Low GCNs of C4T (C4T=2+3) and C4A deficiency (C4A=0+1) were strongly correlated with increased risk of IIM with OR equalled to 2.58 (2.28-2.91), p=5.0×10-53 for C4T, and 2.82 (2.48-3.21), p=7.0×10-57 for C4A deficiency. Contingency and regression analyses showed that among patients with C4A deficiency, the presence of HLA-DR3 became insignificant as a risk factor in IIM except for inclusion body myositis (IBM), by which 98.2% had HLA-DR3 with an OR of 11.02 (1.44-84.4). Intragroup analyses of patients with IIM for C4 protein levels and IIM-related autoantibodies showed that those with anti-Jo-1 or with anti-PM/Scl had significantly lower C4 plasma concentrations than those without these autoantibodies. CONCLUSIONS: C4A deficiency is relevant in dermatomyositis, HLA-DRB1*03 is important in IBM and both C4A deficiency and HLA-DRB1*03 contribute interactively to risk of polymyositis.

Urine proteomics by mass spectrometry identifies proteins involved in key pathogenic pathways in patients with juvenile dermatomyositis.

OBJECTIVES: To identify and validate biomarkers in JDM patients using a multiplexing tandem mass tag urine proteome profiling approach. METHODS: First morning void urine samples were collected from JDM patients (n = 20) and healthy control subjects (n = 21) and processed for analysis using a standardized liquid chromatography-tandem mass spectrometry approach. Biomarkers with significantly altered levels were correlated with clinical measures of myositis disease activity and damage. A subset of candidate biomarkers was validated using commercially available ELISA kits. RESULTS: In total, 2348 proteins were detected in the samples, with 275 proteins quantified across all samples. Among the differentially altered proteins, cathepsin D and galectin-3 binding protein were significantly increased in the urine of JDM patients (adjusted P < 0.05), supporting previous findings in myositis patients. These two candidate biomarkers were confirmed with ELISAs. Cathepsin D positively correlated with Myositis Damage Index (r = 0.57, P < 0.05) and negatively correlated with the Childhood Myositis Assessment Scale (r = -0.54, P < 0.05). We also identified novel JDM candidate biomarkers involved with key features of myositis, including extracellular matrix remodelling proteins. CONCLUSION: This study confirmed the presence of several proteins in the urine of JDM patients that were previously found to be elevated in the blood of myositis patients and identified novel candidate biomarkers that require validation. These results support the use of urine as a source for biomarker development in JDM.

Association of anti-TPM4 autoantibodies with vasculopathic cutaneous manifestations in juvenile dermatomyositis.

OBJECTIVES: AECAs are detected in multiple forms of vasculitis or vasculopathy, including JDM. High levels of tropomyosin alpha-4 chain (TPM4) gene expression in cutaneous lesions and TPM4 protein expression in some endothelial cells (ECs) have been proven. Furthermore, the presence of autoantibodies to tropomyosin proteins have been discovered in DM. We therefore investigated whether anti-TPM4 autoantibodies are an AECA in JDM and are correlated with clinical features of JDM. METHODS: The expression of TPM4 protein in cultured normal human dermal microvascular ECs was investigated by Western blotting. Plasma samples from 63 children with JDM, 50 children with polyarticular JIA (pJIA) and 40 healthy children (HC) were tested for the presence of anti-TPM4 autoantibodies using an ELISA. Clinical features were compared between JDM patients with and without anti-TPM4 autoantibodies. RESULTS: Autoantibodies to TPM4 were detected in the plasma of 30% of JDM, 2% of pJIA (P < 0.0001) and 0% of HC (P < 0.0001). In JDM, anti-TPM4 autoantibodies were associated with the presence of cutaneous ulcers (53%; P = 0.02), shawl sign rash (47%; P = 0.03), mucous membrane lesions (84%; P = 0.04) and subcutaneous edema (42%; P < 0.05). Anti-TPM4 autoantibodies significantly correlated with the use of intravenous steroids and IVIG therapy in JDM (both P = 0.01). The total number of medications received was higher in patients with anti-TPM4 autoantibodies (P = 0.02). CONCLUSION: Anti-TPM4 autoantibodies are detected frequently in children with JDM and are novel myositis-associated autoantibodies. Their presence correlates with vasculopathic and other cutaneous manifestations of JDM that may be indicative of more refractory disease.

A novel estrogen receptor 1: sphingomyelin phosphodiesterase acid-like 3B pathway mediates rituximab response in myositis patients.

OBJECTIVES: The B-cell depleting biologic, rituximab, is used to treat refractory autoimmune myositis. However, the beneficial effects of rituximab appear to outweigh the known contribution of B cells in myositis. We aimed to elucidate how myositis patients respond differently to rituximab and possible alternative mechanisms of action. METHODS: Here we have: (i) comprehensively investigated concurrent mRNA and microRNA expression in muscle biopsies taken at baseline and 16 weeks post treatment in 10 patients who were part of the rituximab in myositis (RIM) trial; and (ii) investigated the beneficial effect of rituximab on myositis muscle cells. RESULTS: Our analyses identified an increased number of changes in gene expression in biopsies from patients who had a clinical response to rituximab (n = 5) compared with non-responders (n = 5). The two groups had completely different changes in microRNA and mRNA expression following rituximab therapy, with the exception of one mRNA, BHMT2. Networks of mRNA and microRNA with opposite direction of expression changes highlighted ESR1 as upregulated in responders. We confirmed ESR1 upregulation upon rituximab treatment of immortalized myotubes and primary human dermatomyositis muscle cells in vitro, demonstrating a direct effect of rituximab on muscle cells. Notably, despite showing a response to rituximab, human dermatomyositis primary muscle cells did not express the rituximab target, CD20. However, these cells expressed a possible alternative target of rituximab, sphingomyelinase-like phosphodiesterase 3 b (SMPDL3B). CONCLUSION: In addition to B-cell depletion, rituximab may be beneficial in myositis due to increased ESR1 signalling mediated by rituximab binding to SMPDL3B on skeletal muscle cells.

Anti-FHL1 autoantibodies in juvenile myositis are associated with anti-Ro52 autoantibodies but not with severe disease features.

OBJECTIVES: Four-and-a-half LIM domains 1 (FHL1) is a muscle-specific protein. Autoantibodies against FHL1 were recently discovered in adults with idiopathic inflammatory myopathies (IIMs) and were found to be associated with clinical features and outcomes indicative of increased disease severity. Anti-FHL1 autoantibodies have not been described in children. Here, the prevalence and clinical features associated with anti-FHL1 autoantibodies were examined in a large North American cohort of juvenile patients with IIM. METHODS: Sera from 338 juvenile IIM patients and 91 juvenile healthy controls were screened for anti-FHL1 autoantibodies by ELISA. Clinical characteristics and HLA alleles of those with and without anti-FHL1 autoantibodies were compared among those with juvenile IIM. RESULTS: Anti-FHL1 autoantibodies were present in 10.9% of juvenile IIM patients and 1.1% of controls. The frequency of anti-FHL1 autoantibodies among clinical and serologic subgroups did not differ. A higher percentage of Asian patients had anti-FHL1 autoantibodies (11% vs 0.7%; P = 0.002). Myositis-associated autoantibodies (MAAs) [odds ratio (OR) 2.09 (CI 1.03, 4.32)], anti-Ro52 autoantibodies specifically [OR 4.17 (CI 1.83, 9.37)] and V-sign rash [OR 2.59 (CI 1.22, 5.40)] were associated with anti-FHL1 autoantibodies. There were no differences in other features or markers of disease severity. No HLA associations with anti-FHL1 autoantibodies in Caucasian myositis patients were identified. CONCLUSION: Anti-FHL1 autoantibodies are present in ∼11% of juvenile IIM patients and commonly co-occur with MAAs, including anti-Ro52 autoantibodies. In contrast to adult IIM, anti-FHL1 autoantibodies in juvenile myositis are associated with V-sign rash but not with other distinctive clinical features or worse outcomes.

Performance of the 2016 ACR-EULAR myositis response criteria in juvenile dermatomyositis therapeutic trials and consensus profiles.

OBJECTIVES: The 2016 ACR-EULAR Response Criteria for JDM was developed as a composite measure with differential weights of six core set measures (CSMs) to calculate a Total Improvement Score (TIS). We assessed the contribution of each CSM, representation of muscle-related and patient-reported CSMs towards improvement, and frequency of CSM worsening across myositis response criteria (MRC) categories in validation of MRC. METHODS: Data from JDM patients in the Rituximab in Myositis trial (n = 48), PRINTO JDM trial (n = 139), and consensus patient profiles (n = 273) were included. Observed vs expected CSM contributions were compared using Sign test. Characteristics of MRC categories were compared by Wilcoxon tests with Bonferroni adjustment. Spearman correlation of changes in TIS and individual CSMs were examined. Agreement between physician-assessed change and MRC categories was evaluated by weighted Cohen's kappa. RESULTS: Of 457 JDM patients with IMACS CSMs and 380 with PRINTO CSMs, 9-13% had minimal, 19-23% had moderate and 41-50% had major improvement. The number of improved and absolute percentage change of CSMs increased by MRC improvement level. Patients with minimal improvement by MRC had a median of 0-1 CSM worsened, and those with moderate/major improvement had a median of zero worsening CSMs. Of patients improved by MRC, 94-95% had improvement in muscle strength and 93-95% had improvement in ≥1 patient-reported CSM. IMACS and PRINTO CSMs performed similarly. Physician-rated change and MRC improvement categories had moderate-to-substantial agreement (Kappa 0.5-0.7). CONCLUSION: The ACR-EULAR MRC perform consistently across multiple studies, supporting its further use as an efficacy end point in JDM trials.

Performance of the 2016 ACR-EULAR Myositis Response Criteria in adult dermatomyositis/polymyositis therapeutic trials and consensus profiles.

OBJECTIVE: The ACR-EULAR Myositis Response Criteria (MRC) were developed as a composite measure using absolute percentage change in six core set measures (CSMs). We aimed to further validate the MRC by assessing the contribution of each CSM, frequency of strength vs extramuscular activity improvement, representation of patient-reported outcome measures (PROM), and frequency of CSM worsening. METHODS: Data from adult dermatomyositis/polymyositis patients in the rituximab (n = 147), etanercept (n = 14), and abatacept (n = 19) trials, and consensus patient profiles (n = 232) were evaluated. The Total Improvement Score (TIS), number of improving vs worsening CSMs, frequency of improvement with and without muscle-related CSMs, and contribution of PROM were evaluated by MRC category. Regression analysis was performed to assess contribution of each CSM to the MRC. RESULTS: Of 412 adults with dermatomyositis/polymyositis, there were 37%, 24%, 25%, and 14% with no, minimal, moderate, and major MRC improvement, respectively. The number of improving CSMs and absolute percentage change in all CSMs increased by improvement category. In minimal-moderate improvement, only physician-reported disease activity contributed significantly more than expected by MRC. Of patients with at least minimal improvement, 95% had improvement in muscle-related measures and a majority (84%) had improvement in PROM. Patients with minimal improvement had worsening in a median of 1 CSM, and most patients with moderate-major improvement had no worsening CSMs. Physician assessment of change generally agreed with MRC improvement categories. CONCLUSION: The ACR-EULAR MRC performs consistently across multiple studies, further supporting its use as an efficacy end point in future myositis therapeutic trials.

Preliminary validation of muscle ultrasound in juvenile dermatomyositis (JDM).

OBJECTIVE: To compare muscle ultrasound (MUS) parameters in patients with juvenile JDM and healthy controls, and examine their association with JDM disease activity measures and MRI. METHODS: MUS of the right mid-rectus femoris was performed in 21 patients with JDM meeting probable or definite Bohan and Peter criteria and 28 demographically matched healthy control subjects. MUS parameters were quantitated by digital image processing and correlated with JDM disease activity measures and semi-quantitative thigh MRI short tau inversion recovery (STIR) and T1 scores. RESULTS: Rectus femoris MUS echogenicity was increased (median 47.8 vs 38.5, P = 0.002) in patients with JDM compared with controls. Rectus femoris MUS echogenicity correlated with Physician Global Activity (PGA), Manual Muscle Testing (MMT), and Childhood Myositis Assessment Scale (CMAS) (rs 0.4-0.54). Some MUS parameters correlated with functional quantitative measures of muscle strength: resting RF area on MUS strongly correlated with knee extension quantitative muscle testing (rs 0.76), and contracted area correlated with proximal MMT, knee extension quantitative muscle testing, and CMAS (rs 0.71-0.80). MUS echogenicity correlated with both STIR and T1 MRI (rs 0.43), and T1 MRI correlated inversely with RF contracted area (rs -0.49) on MUS. There were differences in pre- and post-exercise vascular power and colour Doppler on MUS in patients with JDM vs controls, with the percentage change of post-exercise vascular power Doppler lower in JDM compared with controls (7.1% vs 100.0%). CONCLUSIONS: These data suggest MUS may be a valuable imaging modality to assess JDM disease activity and damage.

Association of anti-HSC70 autoantibodies with cutaneous ulceration and severe disease in juvenile dermatomyositis.

OBJECTIVES: JDM is an inflammatory myopathy characterized by prominent vasculopathy. AECAs are frequently detected in inflammatory and autoimmune diseases. We sought to determine whether AECAs correlate with clinical features of JDM, and thus serve as biomarkers to guide therapy or predict outcome. METHODS: Plasma samples from 63 patients with JDM, 49 patients with polyarticular JIA and 40 juvenile healthy controls were used to detect anti-heat shock cognate 71 kDa protein (HSC70) autoantibodies, a newly identified AECA, in ELISA assays. Clinical features were compared between JDM patients with and without anti-HSC70 autoantibodies. RESULTS: Anti-HSC70 autoantibodies were detected in 35% of patients with JDM, in 0% of patients with JIA (P < 0.0001) and in 0% of healthy donors (P < 0.0001). Both the presence of cutaneous ulcers (59% vs 17%, P < 0.002) and the use of wheelchairs and/or assistive devices (64% vs 27%, P < 0.007) were strongly associated with anti-HSC70 autoantibodies in JDM. High scores on the severity of myositis damage measures at the time of measurement of anti-HSC70 autoantibodies and an increased number of hospitalizations were also associated with anti-HSC70 autoantibodies. Intravenous immunoglobulin therapy was used more often in anti-HSC70 autoantibody-positive patients. CONCLUSION: Anti-HCS70 autoantibodies are detected frequently in children with JDM and are novel myositis-associated autoantibodies correlating with disease severity.

Baseline factors associated with self-reported disease flares following COVID-19 vaccination among adults with systemic rheumatic disease: results from the COVID-19 global rheumatology alliance vaccine survey.

OBJECTIVE: To examine the frequency of, and risk factors for, disease flare following COVID-19 vaccination in patients with systemic rheumatic disease (SRD). METHODS: An international study was conducted from 2 April to 16 August 2021, using an online survey of 5619 adults with SRD for adverse events following COVID-19 vaccination, including flares of disease requiring a change in treatment. We examined risk factors identified a priori based on published associations with SRD activity and SARS-CoV-2 severity, including demographics, SRD type, comorbidities, vaccine type, cessation of immunosuppressive medications around vaccination and history of reactions to non-COVID-19 vaccines, using multivariable logistic regression. RESULTS: Flares requiring a change in treatment following COVID-19 vaccination were reported by 4.9% of patients. Compared with rheumatoid arthritis, certain SRD, including systemic lupus erythematosus (OR 1.51, 95% CI 1.03, 2.20), psoriatic arthritis (OR 1.95, 95% CI 1.20, 3.18) and polymyalgia rheumatica (OR 1.94, 95% CI 1.08, 2.48) were associated with higher odds of flare, while idiopathic inflammatory myopathies were associated with lower odds for flare (OR 0.54, 95% CI 0.31-0.96). The Oxford-AstraZeneca vaccine was associated with higher odds of flare relative to the Pfizer-BioNTech vaccine (OR 1.44, 95% CI 1.07, 1.95), as were a prior reaction to a non-COVID-19 vaccine (OR 2.50, 95% CI 1.76, 3.54) and female sex (OR 2.71, 95% CI 1.55, 4.72). CONCLUSION: SRD flares requiring changes in treatment following COVID-19 vaccination were uncommon in this large international study. Several potential risk factors, as well as differences by disease type, warrant further examination in prospective cohorts.

Anti-MDA5 autoantibodies associated with juvenile dermatomyositis constitute a distinct phenotype in North America.

OBJECTIVE: Myositis-specific autoantibodies have defined distinct phenotypes of patients with juvenile myositis (JIIM). We assessed the frequency and clinical significance of anti-melanoma differentiation-associated gene 5 (MDA5) autoantibody-associated JIIM in a North American registry. METHODS: Retrospective examination of the characteristics of 35 JIIM patients with anti-MDA5 autoantibodies was performed, and differences from other myositis-specific autoantibody groups were evaluated. RESULTS: Anti-MDA5 autoantibodies were present in 35/453 (7.7%) of JIIM patients and associated with older age at diagnosis, and lower serum creatine kinase and aldolase levels. Patients with anti-MDA5 autoantibodies had more frequent weight loss, adenopathy, arthritis, interstitial lung disease (ILD), and less frequent falling compared with anti-transcriptional intermediary factor 1 (TIF1), anti-nuclear matrix protein 2 (NXP2) and myositis-specific autoantibody/myositis-associated autoantibody-negative patients. They had a different season of diagnosis and less frequent mechanic's hands and ILD compared with those with anti-synthetase autoantibodies. Anti-MDA5 patients received fewer medications compared with anti-TIF1, and corticosteroid treatment was shorter compared with anti-TIF1 and anti-nuclear matrix protein 2 autoantibody groups. The frequency of remission was higher in anti-MDA5 than anti-synthetase autoantibody-positive JIIM. In multivariable analyses, weight loss, arthritis and arthralgia were most strongly associated with anti-MDA5 autoantibody-positive JIIM. CONCLUSION: Anti-MDA5 JIIM is a distinct subset, with frequent arthritis, weight loss, adenopathy and less severe myositis, and is also associated with ILD. Anti-MDA5 is distinguished from anti-synthetase autoantibody-positive JIIM by less frequent ILD, lower creatine kinase levels and differing seasons of diagnosis. Anti-MDA5 has comparable outcomes, but with the ability to discontinue steroids more rapidly and less frequent flares compared with anti-TIF1 autoantibodies, and more frequent remission compared with anti-synthetase JIIM patients.

Corticosteroid discontinuation, complete clinical response and remission in juvenile dermatomyositis.

OBJECTIVE: A North American registry of JDM patients was examined for frequency of and factors associated with corticosteroid discontinuation, complete clinical response and remission. METHODS: We evaluated probability of achieving final corticosteroid discontinuation, complete clinical response and remission in 307 JDM patients by Weibull time-to-event modelling; conditional probability of complete clinical response and remission using Bayesian network modelling; and significant predictors with multivariable Markov chain Monte-Carlo Weibull extension models. RESULTS: The probability of corticosteroid discontinuation was 56%, complete clinical response 38% and remission 30% by 60 months after initial treatment in 105 patients. The probability of remission was conditional on corticosteroid discontinuation and complete clinical response. Photosensitivity, contractures and a longer time to complete clinical response were predictive of the time to final corticosteroid discontinuation. Anti-MJ (NXP2) autoantibodies and a Northwest residential geoclimatic zone were predictive of shorter time to complete clinical response, while dysphonia, contractures, an increase in medications within 24 months and a longer time to corticosteroid discontinuation were associated with longer time to complete clinical response. Anti-p155/140 (TIF1) autoantibodies, an increase in medications within 12-24 months, or longer times to corticosteroid discontinuation and complete clinical response were associated with longer time to remission. CONCLUSION: JDM patients achieve favourable outcomes, including corticosteroid discontinuation, complete clinical response and remission, although timelines for these may be several years based on time-dependent analyses. These outcomes are inter-related and strong predictors of each other. Selected clinical features and myositis autoantibodies are additionally associated with these outcomes.

Risk factors associated with Pneumocystis jirovecii pneumonia in juvenile myositis in North America.

OBJECTIVES: Pneumocystis jirovecii pneumonia (PJP) is associated with significant morbidity and mortality in adult myositis patients; however, there are few studies examining PJP in juvenile myositis [juvenile idiopathic inflammatory myopathy (JIIM)]. The purpose of this study was to determine the risk factors and clinical phenotypes associated with PJP in JIIM. METHODS: An research electronic data capture (REDCap) questionnaire regarding myositis features, disease course, medications and PJP infection characteristics was completed by treating physicians for 13 JIIM patients who developed PJP (PJP+) from the USA and Canada. Myositis features and medications were compared with 147 JIIM patients without PJP (PJP-) from similar geographic regions who enrolled in National Institutes of Health natural history studies. RESULTS: PJP+ patients were more often of Asian ancestry than PJP- patients [odds ratio (OR) 8.7; 95% CI 1.3, 57.9]. Anti- melanoma differentiation associated protein 5 (MDA5) autoantibodies (OR 12.5; 95% CI 3.0, 52.4), digital infarcts (OR 43.8; 95% CI 4.2, 460.2), skin ulcerations (OR 12.0; 95% CI 3.5, 41.2) and interstitial lung disease (OR 10.6; 95% CI 2.1, 53.9) were more frequent in PJP+ patients. Before PJP diagnosis, patients more frequently received pulse steroids, rituximab and more immunosuppressive therapy compared with PJP- patients. Seven PJP+ patients were admitted to the intensive care unit and four patients died due to PJP or its complications. CONCLUSIONS: PJP is a severe infection in JIIM that can be associated with mortality. Having PJP was associated with more immunosuppressive therapy, anti-MDA5 autoantibodies, Asian race and certain clinical features, including digital infarcts, cutaneous ulcerations and interstitial lung disease. Prophylaxis for PJP should be considered in juvenile myositis patients with these features.

Anti-Ro52 autoantibodies are associated with interstitial lung disease and more severe disease in patients with juvenile myositis.

OBJECTIVES: Anti-Ro52 autoantibodies are associated with more severe interstitial lung disease (ILD) in adult myositis patients with antiaminoacyl transfer (t)RNA synthetase autoantibodies. However, few studies have examined anti-Ro52 autoantibodies in juvenile myositis. The purpose of this study was to define the prevalence and clinical features associated with anti-Ro52 autoantibodies in a large cohort of patients with juvenile myositis. METHODS: We screened sera from 302 patients with juvenile dermatomyositis (JDM), 25 patients with juvenile polymyositis (JPM) and 44 patients with juvenile connective tissue disease-myositis overlap (JCTM) for anti-Ro52 autoantibodies by ELISA. Clinical characteristics were compared between myositis patients with and without anti-Ro52 autoantibodies. RESULTS: Anti-Ro52 autoantibodies were found in 14% patients with JDM, 12% with JPM and 18% with JCTM. Anti-Ro52 autoantibodies were more frequent in patients with antiaminoacyl tRNA synthetase (64%, p<0.001) and anti-MDA5 (31%, p<0.05) autoantibodies. After controlling for the presence of myositis-specific autoantibodies, anti-Ro52 autoantibodies were associated with the presence of ILD (36% vs 4%, p<0.001). Disease course was more frequently chronic, remission was less common, and an increased number of medications was received in anti-Ro52 positive patients. CONCLUSIONS: Anti-Ro52 autoantibodies are present in 14% of patients with juvenile myositis and are strongly associated with anti-MDA5 and antiaminoacyl tRNA synthetase autoantibodies. In all patients with juvenile myositis, those with anti-Ro52 autoantibodies were more likely to have ILD. Furthermore, patients with anti-Ro52 autoantibodies have more severe disease and a poorer prognosis.

Focused HLA analysis in Caucasians with myositis identifies significant associations with autoantibody subgroups.

OBJECTIVES: Idiopathic inflammatory myopathies (IIM) are a spectrum of rare autoimmune diseases characterised clinically by muscle weakness and heterogeneous systemic organ involvement. The strongest genetic risk is within the major histocompatibility complex (MHC). Since autoantibody presence defines specific clinical subgroups of IIM, we aimed to correlate serotype and genotype, to identify novel risk variants in the MHC region that co-occur with IIM autoantibodies. METHODS: We collected available autoantibody data in our cohort of 2582 Caucasian patients with IIM. High resolution human leucocyte antigen (HLA) alleles and corresponding amino acid sequences were imputed using SNP2HLA from existing genotyping data and tested for association with 12 autoantibody subgroups. RESULTS: We report associations with eight autoantibodies reaching our study-wide significance level of p<2.9×10-5. Associations with the 8.1 ancestral haplotype were found with anti-Jo-1 (HLA-B*08:01, p=2.28×10-53 and HLA-DRB1*03:01, p=3.25×10-9), anti-PM/Scl (HLA-DQB1*02:01, p=1.47×10-26) and anti-cN1A autoantibodies (HLA-DRB1*03:01, p=1.40×10-11). Associations independent of this haplotype were found with anti-Mi-2 (HLA-DRB1*07:01, p=4.92×10-13) and anti-HMGCR autoantibodies (HLA-DRB1*11, p=5.09×10-6). Amino acid positions may be more strongly associated than classical HLA associations; for example with anti-Jo-1 autoantibodies and position 74 of HLA-DRB1 (p=3.47×10-64) and position 9 of HLA-B (p=7.03×10-11). We report novel genetic associations with HLA-DQB1 anti-TIF1 autoantibodies and identify haplotypes that may differ between adult-onset and juvenile-onset patients with these autoantibodies. CONCLUSIONS: These findings provide new insights regarding the functional consequences of genetic polymorphisms within the MHC. As autoantibodies in IIM correlate with specific clinical features of disease, understanding genetic risk underlying development of autoantibody profiles has implications for future research.