Objective. Anti-p155 autoantibody, which was recently described in adult patients with dermatomyositis (DM), seems to be associated with cancer in this population. We performed a systematic review and metaanalysis to ascertain the accuracy of anti-p155 testing for the diagnosis of cancer-associated myositis.Methods. We searched relevant databases, with no restrictions on study design or language, for original studies that included adult patients with probable/ definite DM or amyopathic DM who were evaluated for neoplasm and anti-p155 status. Pooled sensitivity and specificity were calculated using a bivariate model. We computed the diagnostic odds ratio (OR), likelihood ratios (LRs) for positive and negative test results, positive and negative predictive values, and the summary receiver operating characteristic (SROC) curve. Statistical heterogeneity between studies was assessed using the I 2 statistic, and 95% confidence intervals (95% CIs) were computed for the parameters studied.Results. Six studies including a total of 312 adult patients with DM were selected. The pooled sensitivity of anti-p155 for diagnosing cancer-associated DM was 78% (95% CI 45-94%), and specificity was 89% (95% CI 82-93%). The diagnostic OR was 27.26 (95% CI 6.59-112.82), and LRs for positive and negative test results were 6.79 (95% CI 4.11-11.23) and 0.25 (95% CI 0.08-0.76), respectively. Heterogeneity was substantial except with regard to the LR for a positive test result. The area under the SROC curve was 0.91 (95% CI 0.88-0.93). Taking the pooled prevalence of 17% as pretest probability, anti-p155 had a positive predictive value of 58% and a negative predictive value of 95%.Conclusion. Our findings indicate that anti-p155 autoantibody determination is useful for diagnosing cancer-associated myositis and guiding disease management.Idiopathic inflammatory myopathies are a group of systemic diseases that include dermatomyositis (DM), polymyositis, and sporadic inclusion body myositis. An association between cancer and idiopathic inflammatory myopathies, referred to as cancer-associated myositis, has been extensively reported in the medical literature. The overall cancer risk in these patients is higher than that in the age-and sex-matched general population, particularly during the 3 years following the diagnosis of myositis. Patients with DM have the highest risk of associated cancer (1-5). It is believed that almost onethird of DM cases develop as a paraneoplastic phenomenon.Cancer screening is common practice in patients recently diagnosed as having DM, but there is no consensus regarding how and how often screening should be performed. Several clinical and laboratory markers predictive of neoplasm have been proposed to identify patients with cancer-associated myositis in clin-

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ObjectiveActivation of the type 1 interferon (IFN1) pathway is a prominent feature of dermatomyositis (DM) muscle and may play a role in the pathogenesis of this disease. However, the relevance of the IFN1 pathway in patients with other types of myositis such as the antisynthetase syndrome (AS), immune-mediated necrotizing myopathy (IMNM), and inclusion body myositis (IBM) is largely unknown. Moreover, the activation of the type 2 interferon (IFN2) pathway has not been comprehensively explored in myositis. In this cross-sectional study, our objective was to determine whether IFN1 and IFN2 pathways are differentially activated in different types of myositis by performing RNA sequencing on muscle biopsy samples from 119 patients with DM, IMNM, AS, or IBM and on 20 normal muscle biopsies.MethodsThe expression of IFN1- and IFN2-inducible genes was compared between the different groups.ResultsThe expression of IFN1-inducible genes was high in DM, moderate in AS, and low in IMNM and IBM. In contrast, the expression of IFN2-inducible genes was high in DM, IBM, and AS but low in IMNM. The expression of IFN-inducible genes correlated with the expression of genes associated with inflammation and muscle regeneration. Of note, ISG15 expression levels alone performed as well as composite scores relying on multiple genes to monitor activation of the IFN1 pathway in myositis muscle biopsies.ConclusionsIFN1 and IFN2 pathways are differentially activated in different forms of myositis. This observation may have therapeutic implications because immunosuppressive medications may preferentially target each of these pathways.

Introduction Musculoskeletal manifestations are well-recognized side effects of treatment with statins. New advances in this field have appeared in recent years. This review focuses on the diagnosis of these conditions and their underlying pathogenesis, in particular immune-mediated necrotizing myopathy. Areas covered Clinical phenotypes including rhabdomyolysis, myalgia and/or mild hyperCKemia, self-limited toxin statin myopathy, and immune-mediated necrotizing myopathy are herein described. Therapeutic recommendations and a diagnostic algorithm in statin-associated myopathy are also proposed. The etiology and pathogenesis of statin-induced myopathy has mainly focused on the anti-HMGCR antibodies and the responsibility of the immune-mediated necrotizing myopathy is discussed. The fact that patients who have not been exposed to statins may develop statin-associated autoimmune myopathy with anti-HMGCR antibodies is also addressed. The literature search strategy included terms identified by searches of PubMed between 1969 and December 2017. The search terms ‘myositis’, ‘statin-induced autoimmune myopathy’, ‘immunemediate necrotizing myopathy’, ‘statins’, ‘muscular manifestations’, and ‘anti-HMGCR antibodies’ were used. Expert commentary Full characterization of the known phenotypes of statin toxicity and the specific role of the anti-HMGCR in those exposed and not exposed (i.e. juvenile forms) to statins and in some types of neoplasms is of paramount relevance.

ObjectivesMyositis is a heterogeneous family of diseases that includes dermatomyositis (DM), antisynthetase syndrome (AS), immune-mediated necrotising myopathy (IMNM), inclusion body myositis (IBM), polymyositis and overlap myositis. Additional subtypes of myositis can be defined by the presence of myositis-specific autoantibodies (MSAs). The purpose of this study was to define unique gene expression profiles in muscle biopsies from patients with MSA-positive DM, AS and IMNM as well as IBM.MethodsRNA-seq was performed on muscle biopsies from 119 myositis patients with IBM or defined MSAs and 20 controls. Machine learning algorithms were trained on transcriptomic data and recursive feature elimination was used to determine which genes were most useful for classifying muscle biopsies into each type and MSA-defined subtype of myositis.ResultsThe support vector machine learning algorithm classified the muscle biopsies with >90% accuracy. Recursive feature elimination identified genes that are most useful to the machine learning algorithm and that are only overexpressed in one type of myositis. For example, CAMK1G (calcium/calmodulin-dependent protein kinase IG), EGR4 (early growth response protein 4) and CXCL8 (interleukin 8) are highly expressed in AS but not in DM or other types of myositis. Using the same computational approach, we also identified genes that are uniquely overexpressed in different MSA-defined subtypes. These included apolipoprotein A4 (APOA4), which is only expressed in anti-3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) myopathy, and MADCAM1 (mucosal vascular addressin cell adhesion molecule 1), which is only expressed in anti-Mi2-positive DM.ConclusionsUnique gene expression profiles in muscle biopsies from patients with MSA-defined subtypes of myositis and IBM suggest that different pathological mechanisms underly muscle damage in each of these diseases.

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This study analyzed the relationship between the density of intraepidermal nerve fibers (IENF) and the characteristics of either nociceptive laser-evoked potentials (LEPs) or contact heat-evoked potentials (CHEPs) in patients with painful sensory polyneuropathy with the aim to determine which parameters of LEPs and CHEPs more reliably reflect IENF loss. A total of 96 patients and 35 healthy volunteers took part in the study. Based on clinical examination, nerve conduction tests, and quantitative sensory testing, we identified 52 patients with small-fiber neuropathy (SFN), 40 with mixed (small-fiber and large-fiber) neuropathy (MFN), and 4 who were excluded from the analysis because of no evidence of involvement of small fibers. The latency of the N2 was delayed for both LEPs and CHEPs in patients with MFN and for CHEPs only in patients with SFN. The amplitude of the vertex N2/P2 potential was similarly reduced in both types of neuropathy, but LEPs were more frequently absent than CHEPs in MFN patients (68% vs 40%). In general, latency and amplitude of LEPs and CHEPs were well correlated with IENF density. SFN patients were characterized by abnormal EPs and slightly decreased but morphologically abnormal IENF. MFN patients were characterized by frequently absent LEPs and CHEPs and a rather severe IENF loss. The correlation between nociceptive evoked potentials (laser-evoked potentials and contact heat-evoked potentials) and skin biopsy aids in the diagnosis of painful neuropathies.