Abstract

The rarity and heterogeneity of the idiopathic inflammatory myopathies (IIM), and the few validated assessment tools available, have limited information to guide the management of patients with polymyositis, dermatomyositis or inclusion body myositis. In light of the need for such tools, the International Myositis Assessment and Clinical Studies Group (IMACS) was formed as a multidisciplinary consortium of rheumatologists, neurologists, dermatologists, physiatrists and other myositis experts to develop consensus and standards for the conduct and reporting of myositis studies, and to facilitate myositis research. IMACS has developed consensus core set measures of disease activity, disease damage and patient-reported outcomes, and compiled a preliminary definition of improvement. The IMACS tools assist in the evaluation of the extent of disease activity and damage, although other approaches—including key clinical features, laboratory tests, muscle T1 and short τ inversion recovery MRI and immunological markers—are also helpful. Clinical remission is a realistic objective for most patients and should be pursued aggressively to optimise outcomes. Physical therapy and rehabilitation should be applied early and consistently to achieve optimal strength and function. Treatments that have been developed for other immune-mediated diseases are also being used and tested in the IIM, and some have shown anecdotal evidence of benefit. Recent advances in understanding the pathogenesis of myositis, development of assessments and treatments for other diseases that can be applied to myositis, and international collaborations and consensus standards for evaluating the IIM, all promise improvements in the assessment and treatment of myositis in the future.