Calcinosis in juvenile dermatomyositis is influenced by both anti-NXP2 autoantibody status and age at disease onset.

Calcinosis is a major cause of morbidity in JDM and has previously been linked to anti-NXP2 autoantibodies, younger age at disease onset and more persistent disease activity. This study aimed to investigate the clinical associations of anti-NXP2 autoantibodies in patients with JDM stratified by age at disease onset

Anti-MDA5 autoantibodies in juvenile dermatomyositis identify a distinct clinical phenotype: a prospective cohort study.

The aim of this study was to define the frequency and associated clinical phenotype of anti-MDA5 autoantibodies in a large UK based, predominantly Caucasian, cohort of patients with juvenile dermatomyositis (JDM)

Anti-HMGCR Autoantibodies in Juvenile Idiopathic Inflammatory Myopathies Identify a Rare but Clinically Important Subset of Patients

OBJECTIVE: We aimed to establish the prevalence and clinical associations of anti-HMG-CoA-reductase (anti-HMGCR) in a large UK cohort with juvenile myositis. METHODS: There were 381 patients investigated for anti-HMGCR using ELISA. RESULTS: Anti-HMGCR autoantibodies were detected in 4 patients (1%). These children had no or minimal rash and significant muscle disease. Muscle biopsies were considered distinctive, with widespread variation in fiber size, necrotic fibers, and chronic inflammatory cell infiltrates; all had prolonged elevation of creatine kinase and all ultimately received biologic therapies. CONCLUSION: Anti-HMGCR in UK children with myositis are associated with severe disease that is poorly responsive to standard treatment

Muscle biopsy in combination with myositis-specific autoantibodies aids prediction of outcomes in juvenile dermatomyositis

OBJECTIVE: Juvenile dermatomyositis (JDM) is a rare and severe autoimmune condition characterized by rash and proximal muscle weakness. While some patients respond to standard treatment, others do not. We investigated whether histopathology and myositis-specific autoantibodies (MSA) have prognostic significance. // METHODS: Muscle biopsy samples (n=101) from the UK JDM Cohort and Biomarker Study were stained, analyzed and scored. Autoantibodies were measured (n=90) and longitudinal clinical data were collected (median follow-up 4.9 years). Long-term treatment status was modelled using generalized estimating equations. // RESULTS: Muscle biopsy scores differed according to MSA. When effects of MSA were accounted for, increased severity of muscle pathology predicted increased risk of remaining on treatment over time: 1.48-fold higher odds (1.12-1.96, p=0.0058) for the global pathology score (hVAS) and 1.10-fold higher odds (1.01-1.21, p=0.038) for the total biopsy score for the standardized score tool. A protective effect was identified in patients with anti-Mi2 autoantibodies, who had 7.06-fold lower odds (1.41-35.36, p=0.018) of remaining on treatment, despite displaying more severe muscle pathology at biopsy. For patients with anti-NXP-2, anti-TIF1γ autoantibodies or no-detectable autoantibody, increased severity of muscle pathology alone could predict the risk of remaining on treatment, without adjustment for MSA: 1.61-fold higher odds (1.16-2.22, p=0.0040) for hVAS and 1.13-fold higher odds (1.03-1.24, p=0.013) for total biopsy score. // CONCLUSION: Muscle pathology, in combination with MSA, predicts the risk of remaining on treatment in JDM and may be useful for discussing probable treatment length with parents and patients. Understanding these associations may identify patients at greater risk of severe disease

The EuroMyositis registry: an international collaborative tool to facilitate myositis research

AIMS: The EuroMyositis Registry facilitates collaboration across the idiopathic inflammatory myopathy (IIM) research community. This inaugural report examines pooled Registry data. METHODS: Cross-sectional analysis of IIM cases from 11 countries was performed. Associations between clinical subtypes, extramuscular involvement, environmental exposures and medications were investigated. RESULTS: Of 3067 IIM cases, 69% were female. The most common IIM subtype was dermatomyositis (DM) (31%). Smoking was more frequent in connective tissue disease overlap cases (45%, OR 1.44, 95% CI 1.09 to 1.90, p=0.012). Smoking was associated with interstitial lung disease (ILD) (OR 1.32, 95% CI 1.06 to 1.65, p=0.013), dysphagia (OR 1.43, 95% CI 1.16 to 1.77, p=0.001), malignancy ever (OR 1.78, 95% CI 1.36 to 2.33, p<0.001) and cardiac involvement (OR 2.40, 95% CI 1.60 to 3.60, p<0.001).Dysphagia occurred in 39% and cardiac involvement in 9%; either occurrence was associated with higher Health Assessment Questionnaire (HAQ) scores (adjusted OR 1.79, 95% CI 1.43 to 2.23, p<0.001). HAQ scores were also higher in inclusion body myositis cases (adjusted OR 3.85, 95% CI 2.52 to 5.90, p<0.001). Malignancy (ever) occurred in 13%, most commonly in DM (20%, OR 2.06, 95% CI 1.65 to 2.57, p<0.001).ILD occurred in 30%, most frequently in antisynthetase syndrome (71%, OR 10.7, 95% CI 8.6 to 13.4, p<0.001). Rash characteristics differed between adult-onset and juvenile-onset DM cases ('V' sign: 56% DM vs 16% juvenile-DM, OR 0.16, 95% CI 0.07 to 0.36, p<0.001). Glucocorticoids were used in 98% of cases, methotrexate in 71% and azathioprine in 51%. CONCLUSION: This large multicentre cohort demonstrates the importance of extramuscular involvement in patients with IIM, its association with smoking and its influence on disease severity. Our findings emphasise that IIM is a multisystem inflammatory disease and will help inform prognosis and clinical management of patients

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

Transcriptional profiling identifies differential expression of long non-coding RNAs in Jo-1 associated and inclusion body myositis.

Myositis is characterised by muscle inflammation and weakness. Although generally thought to be driven by a systemic autoimmune response, increasing evidence suggests that intrinsic changes in the muscle might also contribute to the pathogenesis. Long non-coding RNAs (lncRNAs) are a family of novel genes that regulate gene transcription and translation. To determine the potential role of lncRNAs, we employed next generation sequencing to examine the transcriptome in muscle biopsies obtained from two histologically distinct patient populations, inclusion body myositis (IBM) and anti-Jo-1-associated myositis (Jo-1). 1287 mRNAs and 1068 mRNAs were differentially expressed in the muscle from Jo-1 and IBM patients, respectively. Pathway analysis showed the top canonical pathway in both Jo-1 and IBM was oxidative phosphorylation and mitochondrial dysfunction. We identified 731 known and 325 novel lncRNAs in the muscles biopsies. Comparison with controls showed 55 and 46 lncRNAs were differentially expressed in IBM and Jo-1 myositis, respectively. Of these, 16 lncRNAs were differentially expressed in both IBM and Jo-1 myositis and included upregulated H19, lncMyoD and MALAT1. Given that these are known to regulate muscle proliferation and differentiation, we speculate that changes in lncRNAs might contribute to the phenotypic changes in Jo-1 and IBM myositis