Idiopathic inflammatory myopathy: management and prognosis

Inhibition of myogenic microRNAs 1, 133, and 206 by inflammatory cytokines links inflammation and muscle degeneration in adult inflammatory myopathies

OBJECTIVE

The molecular basis of inflammatory myopathies such as dermatomyositis (DM), polymyositis, and inclusion body myositis, which share the characteristics of chronic muscle inflammation and skeletal muscle wasting, are poorly understood. As such, effective targeted treatments for these diseases are lacking, resulting in critical unmet medical needs for these devastating diseases. The purpose of this study was to identify possible new targets for drug development by exploring the mechanism by which inflammation may play a role in the pathology of the inflammatory myopathies.

METHODS

We compared expression levels of inflammatory cytokines and microRNAs (miRNAs) between muscle biopsy samples from patients with inflammatory myopathies and those from donors without myositis. In vitro human and mouse model systems were then used to characterize the role of these cytokines and microRNAs on myoblast-to-myocyte differentiation.

RESULTS

We observed increased expression of inflammatory cytokines, including tumor necrosis factor α (TNFα), interferon-α (IFNα), IFNβ, and interleukin-1β, in different subtypes of inflammatory myopathies. We observed decreased expression of microRNA-1 (miR-1), miR-133a, and miR-133b in all of the inflammatory myopathy subtypes we evaluated, as well as decreased expression of miR-206 in DM; these miRNAs are essential for adult skeletal muscle differentiation and maintenance. TNFα was significantly inversely correlated with decreased myogenic miRNA expression in the inflammatory myopathy subtypes. In mechanistic studies, TNFα inhibited the expression of myogenic miRNAs and suppressed the differentiation of C2C12 myoblasts to myocytes/myotubes in an NF-κB-dependent manner. This block in differentiation by TNFα was relieved by overexpression of miR-1, miR-206, or miR-133a/b.

CONCLUSION

Taken together, these results provide a new mechanistic link between the action of proinflammatory cytokines and the degenerative pathology of inflammatory myopathies, and suggest therapeutic approaches for these diseases.

Pharyngeal dysphagia in inflammatory muscle diseases resulting from impaired suprahyoid musculature

Dysphagia has previously been reported in the inflammatory myopathies (IMs): inclusion body myositis (IBM), dermatomyositis (DM), and polymyositis (PM). Patients report coughing, choking, and bolus sticking in the pharynx. Myotomy has been the treatment of choice, with variable success reported. We sought to determine underlying causes of dysphagia in IM patients using instrumental evaluation. Eighteen subjects participated in the study: four with DM, six with PM, and eight with IBM. They underwent simultaneous videofluoroscopy and manometry, yielding 214 swallows for analysis regarding function of the upper esophageal sphincter (UES), swallow initiation, hyolaryngeal excursion, and pharyngeal residue. Penetration and aspiration were also recorded. UES failed to relax in two participants. High incidence of pharyngeal dysphagia was noted; 72% of participants demonstrated abnormalities, including delayed swallow initiation (24%), decreased hyolaryngeal excursion (22%), pyriform residue (17%), and penetration (22%). Dysphagia in IM patients appears to be more due to impaired muscle contraction and reduced hyolaryngeal excursion than the often held belief of failed UES relaxation. The distinction between mechanisms causing patients' dysphagia should be examined, particularly if CP myotomy is being considered as it may be contraindicated for patients with normal UES relaxation. More studies investigating IM patients pre- and post-myotomy are needed.

Idiopathic inflammatory myopathies: definition and management of refractory disease

Adult idiopathic inflammatory myopathies, commonly referred to as myositis, are a heterogeneous group of diseases with an autoimmune etiology. In this review, the authors are going to focus on myositis excluding inclusion body myositis. They will review the prognostic factors (for mortality and response to steroids), define refractory disease, introduce a new concept (presumed refractory disease), analyze definitions of active disease, damage and improvement criteria, and summarize therapeutic alternatives for refractory patients, based on different disease phenotypes.

The treatment and prognosis of dermatomyositis: an updated review

Dermatomyositis (DM) is an idiopathic inflammatory myopathy. The mainstay of treatment for DM is oral corticosteroids. However, the dose and length of treatment is debated. Adding to the confusion, there have been no randomized controlled studies comparing the use of various corticosteroid doses and taper rates, and no controlled long-term studies assessing the hypothesis that, unlike systemic lupus erythematous, patients with DM can often achieve long-term remission off therapy. This literature review supports an approach that prednisone should be started at about 1 mg/kg/d, which is then tapered slowly based on the response. As patients respond differently to prednisone, additional therapies may be necessary. When to initiate these therapies requires clinical judgment. In addition, as we learn more about the pathophysiology of DM, newer medications that target specific mechanisms in the immune response may help us better treat the disease. Evidence-based data with long-term follow-up will allow for selection of the best treatment to maximize long-term remission, not simply short-term lowering of the systemic corticosteroid dose.

Novel classification of idiopathic inflammatory myopathies based on overlap syndrome features and autoantibodies: analysis of 100 French Canadian patients

Our objective was to improve the currently imperfect classifications of idiopathic inflammatory myopathies (IIM). In clinical practice, overlap features are common in IIM. This provided a rationale for positioning overlap clinical features at the core of a new classification system. We conducted a longitudinal study of 100 consecutive adult French Canadian patients with IIM. Clinical and laboratory data were obtained by retrospective chart review. Sera were analyzed for autoantibodies (aAbs) by protein A-assisted immunoprecipitation and double immunodiffusion. Overlap aAbs encompassed aAbs to synthetases, systemic sclerosis-associated aAbs, anti-signal recognition particle (SRP) and anti-nucleoporins. Patients were classified both at IIM diagnosis, based on data at presentation, and at the end of follow-up, based on cumulative findings. Three classifications were used: 1) the Bohan and Peter original classification, 2) a new version of that classification as modified by us, and 3) a novel clinicoserologic classification. As investigators were blinded to aAb results, the modified classification is strictly a clinical classification. Its core concept is the attribution of diagnostic significance to the presence of overlap features, that is, their presence resulted in a diagnosis of overlap myositis (OM). This approach allowed direct comparison with the original Bohan and Peter classification. By integrating aAb results to the modified classification, we also defined the clinicoserologic classification, which allowed to examine the added value of aAbs to diagnostic, therapeutic and prognostic stratification. Whereas polymyositis (PM) was the most common IIM according to the original classification, accounting for 45% of the cohort at diagnosis, its frequency fell to 14% with the modified classification. Conversely, while the frequency of myositis associated with connective tissue disease was 24% according to the original classification, the frequency of OM was 60% when using the modified classification. At last follow-up, the frequency of PM fell further to only 9%, while the frequency of OM rose to 67%. Systemic sclerosis was the most common connective tissue disease associated with IIM, accounting for 42.6% of OM patients and 29% of the cohort. The frequencies of overlap aAbs in the cohort and in OM patients were 48% and 70.5% (n =48/68), respectively. The presence of overlap aAbs at IIM diagnosis identified additional OM patients unrecognized by the modified classification. The sensitivity of the modified classification for OM at diagnosis was 87%, suggesting that clinicians may rely on the modified classification for identification of most OM patients, while awaiting results of aAb assays. The new classifications predicted the response to prednisone and IIM course. Using stringent definitions, IIM was classified as responsive or refractory after an adequate initial corticosteroid therapy, and the disease course as monophasic or chronic after a single adequate trial of prednisone. PM was always chronic and was associated with the highest rate (50%) of refractoriness to initial corticosteroid treatment. Dermatomyositis was almost always chronic (92% rate); however, its responsiveness to initial corticosteroid treatment was high (87%). OM was almost always responsive to corticosteroids (89%-100% rates). When OM patients were divided according to aAb subsets, anti-synthetase, SRP, or nucleoporin aAbs were markers for chronic myositis, whereas aAbs to U1RNP, Pm-Scl, or Ku were markers for monophasic myositis. We conclude that the original Bohan and Peter classification should be abandoned as it leads to misclassification of patients. Much of IIM is composed of OM. The proposed modified and clinicoserologic classifications have diagnostic, prognostic, and therapeutic value.

Life-threatening dermatoses due to connective tissue disorders

Connective tissue disorders such as scleroderma, dermatomyositis and lupus erythematosus are autoimmune, multi-system disorders whose clinical manifestations can be restricted to the skin or may involve many organs. The degree and rate of organ system involvement defer, as does the prognosis and rapidity of disease progression. In this article, scleroderma, dermatomyositis and lupus erythematosus will be reviewed in respect to their life-threatening potential.

International consensus on preliminary definitions of improvement in adult and juvenile myositis

OBJECTIVE

To use a core set of outcome measures to develop preliminary definitions of improvement for adult and juvenile myositis as composite end points for therapeutic trials.

METHODS

Twenty-nine experts in the assessment of myositis achieved consensus on 102 adult and 102 juvenile paper patient profiles as clinically improved or not improved. Two hundred twenty-seven candidate definitions of improvement were developed using the experts' consensus ratings as a gold standard and their judgment of clinically meaningful change in the core set of measures. Seventeen additional candidate definitions of improvement were developed from classification and regression tree analysis, a data-mining decision tree tool analysis. Six candidate definitions specifying percentage change or raw change in the core set of measures were developed using logistic regression analysis. Adult and pediatric working groups ranked the 13 top-performing candidate definitions for face validity, clinical sensibility, and ease of use, in which the sensitivity and specificity were >/=75% in adult, pediatric, and combined data sets. Nominal group technique was used to facilitate consensus formation.

RESULTS

The definition of improvement (common to the adult and pediatric working groups) that ranked highest was 3 of any 6 of the core set measures improved by >/=20%, with no more than 2 worse by >/=25% (which could not include manual muscle testing to assess strength). Five and 4 additional preliminary definitions of improvement for adult and juvenile myositis, respectively, were also developed, with several definitions common to both groups. Participants also agreed to prospectively test 6 logistic regression definitions of improvement in clinical trials.

CONCLUSION

Consensus preliminary definitions of improvement were developed for adult and juvenile myositis, and these incorporate clinically meaningful change in all myositis core set measures in a composite end point. These definitions require prospective validation, but they are now proposed for use as end points in all myositis trials.

Polymyositis and dermatomyositis

The inflammatory myopathies, commonly described as idiopathic, are the largest group of acquired and potentially treatable myopathies. On the basis of unique clinical, histopathological, immunological, and demographic features, they can be differentiated into three major and distinct subsets: dermatomyositis, polymyositis, and inclusion-body myositis. Use of new diagnostic criteria is essential to discriminate between them and to exclude other disorders. Dermatomyositis is a microangiopathy affecting skin and muscle; activation and deposition of complement causes lysis of endomysial capillaries and muscle ischaemia. In polymyositis and inclusion-body myositis, clonally expanded CD8-positive cytotoxic T cells invade muscle fibres that express MHC class I antigens, which leads to fibre necrosis via the perforin pathway. In inclusion-body myositis, vacuolar formation with amyloid deposits coexists with the immunological features. The causative autoantigen has not yet been identified. Upregulated vascular-cell adhesion molecule, intercellular adhesion molecule, chemokines, and their receptors promote T-cell transgression, and various cytokines increase the immunopathological process. Early initiation of therapy is essential, since both polymyositis and dermatomyositis respond to immunotherapeutic agents. New immunomodulatory agents currently being tested in controlled trials may prove promising for difficult cases.