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.

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.

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.

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.

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.

Anti-NT5C1A autoantibodies are associated with more severe disease in patients with juvenile myositis.

OBJECTIVES: Autoantibodies recognising cytosolic 5'-nucleotidase 1A (NT5C1A) are found in adult patients with myositis and other autoimmune diseases. They are especially prevalent in adults with inclusion body myositis (IBM), in which they are associated with more severe weakness and higher mortality. This study was undertaken to define the prevalence and clinical features associated with anti-NT5C1A autoantibodies in juvenile myositis. METHODS: We screened sera from 380 patients with juvenile myositis, 30 patients with juvenile idiopathic arthritis (JIA) and 92 healthy control children for anti-NT5C1A autoantibodies. Clinical characteristics were compared between patients with myositis with and without anti-NT5C1A autoantibodies. RESULTS: Anti-NT5C1A autoantibodies were present in 102 of 380 (27%) patients with juvenile myositis and in 11 of 92 (12%) healthy control children (P=0.002) and 27% of children with JIA (P=0.05 vs controls). Sera of 83 of 307 (27%) patients with juvenile dermatomyositis and 16 of 46 (35%) patients with juvenile overlap myositis were anti-NT5C1A autoantibody-positive (P<0.01 vs healthy controls for each), but sera of only 3 of 27 (11%) patients with juvenile polymyositis were anti-NT5C1A-positive. Patients with juvenile myositis with and without anti-NT5C1A autoantibodies had similar clinical phenotypes. However, patients with anti-NT5C1A autoantibody-positive myositis had greater pulmonary symptoms at diagnosis (P=0.005), more frequent hospitalisations (P=0.01) and required a larger number of medications (P<0.001). CONCLUSION: Anti-NT5C1A autoantibodies are present in more than one-quarter of children with juvenile myositis and JIA compared with only 12% of healthy children, suggesting they are myositis-associated in children. As in adults with IBM, patients with juvenile myositis with anti-NT5C1A autoantibodies have more severe disease.

Features distinguishing clinically amyopathic juvenile dermatomyositis from juvenile dermatomyositis.

Objective: We examined features of clinically amyopathic JDM (CAJDM), in which patients have characteristic rashes with little to no evidence of muscle involvement, to determine whether this is a distinct phenotype from JDM. Methods: Demographic, clinical, laboratory and treatment data from 12 (9 hypomyopathic, 3 amyopathic) patients meeting modified Sontheimer criteria for CAJDM and from 60 matched JDM patients meeting Bohan and Peter criteria were examined. Differences were evaluated by Fisher's exact and Mann-Whitney tests, random forests and logistic regression analysis. Results: Nine (75%) CAJDM patients had anti-p155/140 (transcriptional intermediary factor 1), one (8.3%) anti-melanoma differentiation-associated gene 5 autoantibodies and two (16.7%) were myositis autoantibody negative. CAJDM patients were younger at diagnosis and frequently had mild disease at onset. CAJDM patients had less frequent myalgias, arthritis, contractures, calcinosis, dysphagia, abdominal pain and fatigue. The muscle, skeletal and overall clinical scores were lower in CAJDM. Serum muscle enzymes were less frequently increased in CAJDM, and peak values were lower. CAJDM patients received fewer medications compared with JDM patients. Only 50% of CAJDM patients received oral prednisone, but the maximum dose and treatment duration did not differ from JDM. At a median follow-up of 2.9 years, CAJDM patients had no documented functional disability, and none developed weakness, calcinosis, interstitial lung disease or lipodystrophy. Multivariable modelling revealed a lower skeletal score and less frequent myalgias as the most important factors in distinguishing CAJDM from JDM. Conclusion: CAJDM may be distinguished from JDM, in that they often have p155/140 (transcriptional intermediary factor 1) autoantibodies, have fewer systemic manifestations and receive less therapy.

Brief report: ultraviolet radiation exposure is associated with clinical and autoantibody phenotypes in juvenile myositis.

OBJECTIVE: Genetic and environmental factors may contribute to the etiology of the juvenile idiopathic inflammatory myopathies (IIMs), which are systemic autoimmune diseases that are characterized by muscle and skin inflammation. We undertook this study to investigate the association between ultraviolet radiation (UVR) exposure and the clinical and autoantibody expression of juvenile IIM. METHODS: The relationship between UVR exposure in the month before symptom onset and the prevalence of juvenile dermatomyositis (DM), compared to juvenile polymyositis (PM), was assessed in 298 juvenile IIM patients. Among the patients with juvenile DM, the association between UVR exposure and presence of myositis autoantibodies was assessed. Regression models were stratified by sex and race. The association between the regional UV index in US geoclimatic zones and the clinical and autoantibody subgroups was examined by weighted least squares regression analysis. RESULTS: Among girls in this population, the odds of having juvenile DM, compared to juvenile PM, increased per unit increase in the patients' highest UV index in the month before symptom onset (odds ratio [OR] 1.18, 95% confidence interval 1.00-1.40). Moreover, both the mean and highest UV indices were associated with increasing odds of having anti-p155/140 autoantibodies, with the strongest odds in white males (ORs of 1.30 and 1.23, respectively). No association was observed between the UV index and presence of anti-MJ autoantibodies or lack of any myositis autoantibodies. Across all 9 US geoclimatic regions, the mean UV index was associated with increasing odds of having juvenile DM and anti-p155/140 autoantibodies, but decreasing odds of having anti-MJ autoantibodies. CONCLUSION: Short-term UVR exposure prior to illness onset may have a role in the clinical and serologic expression of juvenile myositis. Further research examining the mechanisms of action of UVR in the pathogenesis of juvenile IIM is suggested from these findings.

Myositis-Associated Autoantibodies in Patients With Juvenile Myositis Are Associated With Refractory Disease and Mortality.

OBJECTIVE: Myositis-associated autoantibodies (MAAs) have been associated with overlap myositis, certain disease manifestations such as interstitial lung disease (ILD), and worse prognosis in the idiopathic inflammatory myopathies. MAAs overall remain largely uncharacterized in patients with juvenile-onset myositis. Moreover, it is unknown whether the number of MAAs is associated with disease severity. METHODS: Patients with juvenile myositis in cross-sectional natural history studies who underwent testing for myositis autoantibodies were included. Demographics, myositis autoantibodies, clinical characteristics, medications received, and outcomes of those with and without MAAs were compared. Multivariable logistic regression was performed to determine whether the number of MAAs detected was associated with severe disease features. RESULTS: Among 551 patients, 36% had an MAA and 13% had more than one MAA. Among those who were MAA positive, there was a higher frequency of overlap myositis (18% vs 5.9%, P < 0.001). MAA positivity was associated with certain clinical features, including Raynaud phenomenon (odds ratio [OR] 2.44, 95% confidence interval [CI] 1.41-4.28) and ILD (OR 3.43, 95% CI 1.75-6.96), as well as a chronic disease course (OR 1.72, 95% CI 1.10-2.72) and mortality (OR 3.76, 95% CI 1.72-8.43). The number of MAAs was also associated with mortality (OR 1.83, 95% CI 1.16-2.86). CONCLUSION: MAAs were prevalent in a large cohort of patients with juvenile myositis. ILD, refractory disease, and mortality were associated with MAA positivity. Prospective studies are needed to determine whether early detection of MAAs may lead to improved outcomes for patients with juvenile myositis.

Autoantibodies Recognizing Specificity Protein 4 Co-occur With Anti-Transcription Intermediary Factor 1 and Are Associated With Distinct Clinical Features and Immunogenetic Risk Factors in Juvenile Myositis.

OBJECTIVE: Autoantibodies recognizing specificity protein 4 (Sp4) were recently discovered in adults with idiopathic inflammatory myopathies (IIM). Anti-Sp4 autoantibodies co-occurred in patients with anti-transcription intermediary factor 1 (anti-TIF1) autoantibody-positive dermatomyositis (DM) and were associated with a reduced risk of cancer. In the present study, the prevalence and clinical features associated with anti-Sp4 autoantibodies in juvenile-onset IIM were investigated. METHODS: Serum samples from 336 patients with juvenile myositis in a cross-sectional cohort and 91 healthy controls were screened for anti-Sp4 autoantibodies using enzyme-linked immunosorbent assay. Clinical characteristics, outcomes, and HLA alleles of those with and those without anti-Sp4 autoantibodies were compared. RESULTS: Anti-Sp4 autoantibodies were present in 23 patients (7%) with juvenile myositis and were not present in any of the controls. Anti-Sp4 autoantibodies were found among each clinical myositis subgroup. The frequency of TIF1 autoantibody positivity was significantly higher among those with anti-Sp4 autoantibodies (21 [91%] versus 92 [30%], P < 0.001). In the anti-TIF1 autoantibody-positive subgroup, Raynaud's phenomenon (8 [38%] versus 2 [2%], P < 0.001) was more common and peak aspartate aminotransferase was significantly lower in those with anti-Sp4 autoantibodies. None of the patients with anti-Sp4 autoantibodies required a wheelchair. Among White patients, DQA1*04 and DRB1*08 were associated with anti-Sp4 autoantibodies. CONCLUSION: Anti-Sp4 autoantibodies were found in patients with juvenile-onset IIM, predominantly those with coexisting anti-TIF1 autoantibodies. Patients with anti-Sp4 autoantibodies represent a phenotypic subset of anti-TIF1 autoantibody-positive myositis characterized by frequent Raynaud's phenomenon and less pronounced muscle involvement, similar to adults with these autoantibodies. Novel immunogenetic risk factors for White patients with IIM were identified among juveniles with anti-Sp4 autoantibodies.

Environmental factors associated with juvenile idiopathic inflammatory myopathy clinical and serologic phenotypes.

BACKGROUND: Environmental exposures have been associated with the juvenile idiopathic inflammatory myopathies (JIIM). We undertook a questionnaire-based study to evaluate patient-reported exposures as possible risk factors for JIIM. FINDINGS: One-hundred-seven patients with JIIM were enrolled in a myositis natural history protocol and completed environmental questionnaires. Frequencies of exposures in clinical and myositis-specific autoantibody (MSA) groups were examined. Patients with juvenile dermatomyositis (JDM) and juvenile connective tissue myositis (JCTM) more frequently received an immunization within 1 year of diagnosis compared to juvenile polymyositis (57.5 and 71.4% vs 0.0%, p ≤ 0.017). JCTM patients were more often underweight at diagnosis relative to JDM patients (42.9% vs 7.0%, p = 0.002). MSA-negative patients more frequently had gastroenteritis within a year of diagnosis compared to patients with anti-MDA5 autoantibodies (28.6% vs 0.0%, p = 0.032). Heavy exercise was more frequent in MSA-negative and anti-MDA5 groups compared to the anti-TIF-1 autoantibody group (42.9 and 35.3% vs. 9.0%, p ≤ 0.047). Medications received within 1 year of diagnosis were more frequent in MSA-negative patients relative to those with anti-MDA5 autoantibodies (92.9% vs. 52.8% p = 0.045). Being breastfed > 6 months was more frequent in MSA-negative patients (88.9%) compared to anti-TIF-1 and anti-MDA5 autoantibody groups (41.2 and 28.6%, p ≤ 0.036). CONCLUSIONS: Certain environmental exposures prior to diagnosis differed among clinical and serologic subgroups of JIIM, suggesting additional exposures to be explored as possible risk factors for JIIM phenotypes.

Environmental factors preceding illness onset differ in phenotypes of the juvenile idiopathic inflammatory myopathies.

OBJECTIVE: To assess whether certain environmental factors temporally associated with the onset of juvenile idiopathic inflammatory myopathies (JIIMs) differ between phenotypes. METHODS: Physicians completed questionnaires regarding documented infections, medications, immunizations and an open-ended question about other noted exposures within 6 months before illness onset for 285 patients with probable or definite JIIM. Medical records were reviewed for 81% of the patients. Phenotypes were defined by standard clinical and laboratory measures. RESULTS: Sixty per cent of JIIM patients had a reported exposure within 6 months before illness onset. Most patients (62%) had one recorded exposure, 26% had two and 12% had three to five exposures. Patients older than the median age at diagnosis, those with a longer delay to diagnosis and those with anti-signal recognition particle autoantibodies had a higher frequency of documented exposures [odds ratios (ORs) 95% CI 3.4, 31]. Infections were the most common exposure and represented 44% of the total number of reported exposures. Non-infectious exposures included medications (18%), immunizations (11%), stressful life events (11%) and unusual sun exposure (7%). Exposures varied by age at diagnosis, race, disease course and the presence of certain myositis autoantibodies. CONCLUSION: The JIIMs may be related to multiple exposures and these appear to vary among phenotypes.

Long-term outcomes in Juvenile Myositis patients.

OBJECTIVE: Juvenile idiopathic inflammatory myopathies (JIIM) are rare, chronic autoimmune muscle diseases of childhood, with the potential for significant morbidity. Data on long-term outcomes is limited. In this study we investigate correlations between clinical and demographic features with long-term outcomes in a referral population of adult patients with JIIM. METHODS: Forty-nine adults with JIIM were assessed at two referral centers between 1994 and 2016. Features of active disease and damage at a cross-sectional assessment were obtained. Regression modeling was used to examine factors associated with long-term outcomes, defined by the presence of calcinosis or a higher adjusted Myositis Damage Index (MDI) score. A multivariable model of MDI was constructed using factors that were statistically significant in bivariate models. RESULTS: At a median of 11.5 [IQR 4.5-18.9] years following diagnosis, median American College of Rheumatology (ACR) functional class was 2 [1.5-3.0], Health Assessment Questionnaire (HAQ) score was 0.4 out of 3.0 [0.0-1.0], and manual muscle testing (MMT) score was 229 out of 260 [212.6-256.8]. Median MDI score was 6.0 [3.5-8.9], with the most commonly damaged organ systems being cutaneous and musculoskeletal. Factors associated with an elevated MDI score were the presence of erythroderma and other cutaneous manifestations, disease duration, and ACR functional class. Calcinosis was present in 55% of patients. The strongest predictors of calcinosis were disease duration, periungual capillary changes, and younger age at diagnosis. CONCLUSION: In a tertiary referral population, long-term functional outcomes of JIIM are generally favorable, with HAQ scores indicative of mild disability. Although most patients had mild disease activity and virtually all had significant disease damage, severe or systemic damage was rare. Certain clinical features are associated with long-term damage and calcinosis.

Expression of interferon-regulated genes in juvenile dermatomyositis versus Mendelian autoinflammatory interferonopathies.

BACKGROUND: Juvenile dermatomyositis (JDM) is a systemic autoimmune disease with a prominent interferon (IFN) signature, but the pathogenesis of JDM and the etiology of its IFN signature remain unknown. The Mendelian autoinflammatory interferonopathies, Chronic Atypical Neutrophilic Dermatosis with Lipodystrophy and Elevated temperature (CANDLE) and STING-Associated Vasculopathy with onset in Infancy (SAVI), are caused by genetic mutations and have extremely elevated IFN signatures thought to drive pathology. The phenotypic overlap of some clinical features of CANDLE and SAVI with JDM led to the comparison of a standardized interferon-regulated gene score (IRG-S) in JDM and myositis-specific autoantibody (MSA) JDM subgroups, with CANDLE and SAVI. METHODS: A peripheral 28-component IRG-S assessed by NanoString™ in 57 JDM patients subtyped by MSA was compared with IRG-S in healthy controls (HC) and CANDLE/SAVI patients. Principal component analysis (PCA) was performed, and individual genes were evaluated for their contribution to the score. IRG-S were correlated with disease assessments and patient characteristics. RESULTS: IRG-S in JDM patients were significantly higher than in HC but lower than in CANDLE or SAVI. JDM IRG-S overlapped more with SAVI than CANDLE by PCA. Among MSA groups, anti-MDA5 autoantibody-positive patients' IRG-S overlapped most with SAVI. The IFI27 proportion was significantly higher in SAVI and CANDLE than JDM, but IFIT1 contributed more to IRG-S in JDM. Overall, the contribution of individual interferon-regulated genes (IRG) in JDM was more similar to SAVI. IRG-S correlated moderately with JDM disease activity measures (rs = 0.33-0.47) and more strongly with skin activity (rs = 0.58-0.79) in anti-TIF1 autoantibody-positive patients. Weakness and joint disease activity (multinomial OR 0.91 and 3.3) were the best predictors of high IRG-S. CONCLUSIONS: Our findings demonstrate peripheral IRG expression in JDM overlaps with monogenic interferonopathies, particularly SAVI, and correlates with disease activity. Anti-MDA5 autoantibody-positive JDM IRG-S were notably more similar to SAVI. This may reflect both a shared IFN signature, which is driven by IFN-ß and STING pathways in SAVI, as well as the shared phenotype of vasculopathy in SAVI and JDM, particularly in anti-MDA5 autoantibody-positive JDM, and indicate potential therapeutic targets for JDM.

Statin-induced anti-HMGCR myopathy: successful therapeutic strategies for corticosteroid-free remission in 55 patients.

OBJECTIVE: To describe successful therapeutic strategies in statin-induced anti-HMGCR myopathy. METHODS: Retrospective data from a cohort of 55 patients with statin-induced anti-HMGCR myopathy, sequentially stratified by the presence of proximal weakness, early remission, and corticosteroid and IVIG use at treatment induction, were analyzed for optimal successful induction and maintenance of remission strategies. RESULTS: A total of 14 patients achieved remission with a corticosteroid-free induction strategy (25%). In 41 patients treated with corticosteroids, only 4 patients (10%) failed an initial triple steroid/IVIG/steroid-sparing immunosuppressant (SSI) induction strategy. Delay in treatment initiation was independently associated with lower odds of successful maintenance with immunosuppressant monotherapy (OR 0.92, 95% CI 0.85 to 0.97, P = 0.015). While 22 patients (40%) presented with normal strength, only 9 had normal strength at initiation of treatment. CONCLUSION: While corticosteroid-free treatment of anti-HMGCR myopathy is now a safe option in selected cases, initial triple steroid/IVIG/SSI was very efficacious in induction. Delays in treatment initiation and, as a corollary, delays in achieving remission decrease the odds of achieving successful maintenance with an SSI alone. Avoiding such delays, most notably in patients with normal strength, may reset the natural history of anti-HMGCR myopathy from a refractory entity to a treatable disease.

Immunoprecipitation-western blot for proteins of low abundance.

Combining the procedures of immunoprecipitation and immunoblotting can help to overcome some of the limitations of each separate procedure. Immunoblotting can identify immunoprecipitated proteins more specifically and with higher sensitivity than nonspecific protein stains or autoradiography. Immunoprecipitation can enrich proteins of interest to improve sensitivity for detection when compared with immunoblotting of whole cell extracts. Recently, immunoprecipitation-blotting helped to characterize a new autoantibody, anti-p155, and to test for the presence of the autoantibody in patient sera to study its clinical associations. The procedure for immunoprecipitation-blotting, with specific reference to this autoantibody test ("reverse" immunoprecpitation-blotting), is reported here in detail.

SDS-PAGE for 35S Immunoprecipitation and Immunoprecipitation Western Blotting.

This report discusses recent methods of sample preparation and gel electrophoresis for 35S immunoprecipitation (IP) and IP western blotting. In both methods, IP is used to obtain purified proteins, and sodium dodecyl sulfate polyacrylamide gel electrophoresis is used to separate the proteins on a gel. In 35S IP, the proteins are radiolabeled and visualized on film by fluorography; in IP blotting, proteins are transferred onto nitrocellulose paper, and antibodies are used to detect specific proteins. A similar IP and SDS-PAGE method can be used for both procedures, but IP blotting has the potential advantages of improvement in sensitivity for low-abundance proteins and enhanced specificity for identification of proteins from a mixture. Some of the technical adaptations discussed here to facilitate IP blotting and avoid loss of beads or purified proteins may also be useful for 35S IP.

Predictors of acquired lipodystrophy in juvenile-onset dermatomyositis and a gradient of severity.

We describe the clinical features of 28 patients with juvenile dermatomyositis (JDM) and 1 patient with adult-onset dermatomyositis (DM), all of whom developed lipodystrophy (LD) that could be categorized into 1 of 3 phenotypes, generalized, partial, or focal, based on the pattern of fat loss distribution. LD onset was often delayed, beginning a median of 4.6 years after diagnosis of DM. Calcinosis, muscle atrophy, joint contractures, and facial rash were DM disease features found to be associated with LD. Panniculitis was associated with focal lipoatrophy while the anti-p155 autoantibody, a newly described myositis-associated autoantibody, was more associated with generalized LD. Specific LD features such as acanthosis nigricans, hirsutism, fat redistribution, and steatosis/nonalcoholic steatohepatitis were frequent in patients with LD, in a gradient of frequency and severity among the 3 sub-phenotypes. Metabolic studies frequently revealed insulin resistance and hypertriglyceridemia in patients with generalized and partial LD. Regional fat loss from the thighs, with relative sparing of fat loss from the medial thighs, was more frequent in generalized than in partial LD and absent from DM patients without LD. Cytokine polymorphisms, the C3 nephritic factor, insulin receptor antibodies, and lamin mutations did not appear to play a pathogenic role in the development of LD in our patients. LD is an under-recognized sequela of JDM, and certain DM patients with a severe, prolonged clinical course and a high frequency of calcinosis appear to be at greater risk for the development of this complication. High-risk JDM patients should be screened for metabolic abnormalities, which are common in generalized and partial LD and result in much of the LD-associated morbidity. Further study is warranted to investigate the pathogenesis of acquired LD in patients with DM.

Autoantibodies and their significance in myositis.

Myositis autoantibodies continue to be the subject of substantial interest, with several significant recent developments. Recent studies have emphasized that anti-Jo-1 or other antisynthetases can be associated with interstitial lung disease, even in the absence of myositis. Anti-Jo-1 autoantibody levels were shown to correlate with disease activity over time. Immunization of mice with anti-Jo-1 led to muscle and lung inflammation, reminiscent of human disease. The complexity of the antibody picture in myositis continues to increase. Several new autoantibodies have been described or better characterized. Among these were a new antisynthetase reactive with phenylalanyl-transfer RNA synthetase (anti-Zo); an autoantibody that immunoprecipitates 155- and 140-kD proteins and was common in children but seemed to be associated with malignancy in adults; and an autoantibody to a small ubiquitin-like modifier--activating enzyme associated with dermatomyositis and interstitial lung disease. These findings have significant clinical implications and suggest promising areas of further research.