The Clinical and Histological Spectrum of Idiopathic Inflammatory Myopathies

Idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of myositis, characterised by chronic muscle weakness, cutaneous features, different extra-muscular manifestations and circulating autoantibodies. IIMs included classical polymyositis (PM), dermatomyositis (DM) and other different types of myositis with a wide range of muscle involvement. A complete autoantibody profile and a muscle biopsy are mandatory to correctly diagnose different clinical entities and to define their different prognosis. Bohan and Peter's criteria included five items to diagnose adult onset PM and DM. The sensitivity was 74-100 %, while the specificity is low, due to a poor ability to differentiate PM from neuromuscular diseases. Other criteria included a more accurate histological definition of PM, DM or amyopathic DM, obtaining a higher specificity. Autoantibodies' association, interstitial lung disease and clinical cardiac involvement represent the main items that could define the prognosis of these patients. On the other hand, inclusion body myositis is a different myopathy characterised by a peculiar muscle mass involvement, muscle atrophy and progressive loss of function, due to complete failure to all immunosuppressive drugs used. Treatment of IIMs is based on corticosteroids (CS), which show rapid clinical response and functional improvement. Different immunosuppressant drugs are given to obtain a better control of the disease during CS tapering dose. No controlled double blind trials demonstrated the superiority of one immunesuppressant on another. The occurrence of interstitial lung involvement requires the immediate introduction of immunosuppressants in addiction to CS. Severe dysphagia seems to improve with intravenous immunoglobulins (Ig). Physical therapy could be started after the acute phase of diseases and seems to have a beneficial role in muscle strength recovery.

Treatment for inclusion body myositis

BACKGROUND

Inclusion body myositis (IBM) is a late-onset inflammatory muscle disease (myopathy) associated with progressive proximal and distal limb muscle atrophy and weakness. Treatment options have attempted to target inflammatory and atrophic features of this condition (for example with immunosuppressive and immunomodulating drugs, anabolic steroids, and antioxidant treatments), although as yet there is no known effective treatment for reversing or minimising the progression of inclusion body myositis. In this review we have considered the benefits, adverse effects, and costs of treatment in targeting cardinal effects of the condition, namely muscle atrophy, weakness, and functional impairment.

OBJECTIVES

To assess the effects of treatment for IBM.

SEARCH METHODS

On 7 October 2014 we searched the Cochrane Neuromuscular Disease Group Specialized Register, the Cochrane Central Register for Controlled Trials (CENTRAL), MEDLINE, and EMBASE. Additionally in November 2014 we searched clinical trials registries for ongoing or completed but unpublished trials.

SELECTION CRITERIA

We considered randomised or quasi-randomised trials, including cross-over trials, of treatment for IBM in adults compared to placebo or any other treatment for inclusion in the review. We specifically excluded people with familial IBM and hereditary inclusion body myopathy, but we included people who had connective tissue and autoimmune diseases associated with IBM, which may or may not be identified in trials. We did not include studies of exercise therapy or dysphagia management, which are topics of other Cochrane systematic reviews.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures.

MAIN RESULTS

The review included 10 trials (249 participants) using different treatment regimens. Seven of the 10 trials assessed single agents, and 3 assessed combined agents. Many of the studies did not present adequate data for the reporting of the primary outcome of the review, which was the percentage change in muscle strength score at six months. Pooled data from two trials of interferon beta-1a (n = 58) identified no important difference in normalised manual muscle strength sum scores from baseline to six months (mean difference (MD) -0.06, 95% CI -0.15 to 0.03) between IFN beta-1a and placebo (moderate-quality evidence). A single trial of methotrexate (MTX) (n = 44) provided moderate-quality evidence that MTX did not arrest or slow disease progression, based on reported percentage change in manual muscle strength sum scores at 12 months. None of the fully published trials were adequately powered to detect a treatment effect. We assessed six of the nine fully published trials as providing very low-quality evidence in relation to the primary outcome measure. Three trials (n = 78) compared intravenous immunoglobulin (combined in one trial with prednisone) to a placebo, but we were unable to perform meta-analysis because of variations in study analysis and presentation of trial data, with no access to the primary data for re-analysis. Other comparisons were also reported in single trials. An open trial of anti-T lymphocyte immunoglobulin (ATG) combined with MTX versus MTX provided very low-quality evidence in favour of the combined therapy, based on percentage change in quantitative muscle strength sum scores at 12 months (MD 12.50%, 95% CI 2.43 to 22.57). Data from trials of oxandrolone versus placebo, azathioprine (AZA) combined with MTX versus MTX, and arimoclomol versus placebo did not allow us to report either normalised or percentage change in muscle strength sum scores. A complete analysis of the effects of arimoclomol is pending data publication. Studies of simvastatin and bimagrumab (BYM338) are ongoing. All analysed trials reported adverse events. Only 1 of the 10 trials interpreted these for statistical significance. None of the trials included prespecified criteria for significant adverse events.

AUTHORS' CONCLUSIONS

Trials of interferon beta-1a and MTX provided moderate-quality evidence of having no effect on the progression of IBM. Overall trial design limitations including risk of bias, low numbers of participants, and short duration make it difficult to say whether or not any of the drug treatments included in this review were effective. An open trial of ATG combined with MTX versus MTX provided very low-quality evidence in favour of the combined therapy based on the percentage change data given. We were unable to draw conclusions from trials of IVIg, oxandrolone, and AZA plus MTX versus MTX. We need more randomised controlled trials that are larger, of longer duration, and that use fully validated, standardised, and responsive outcome measures.