Technology insight: tools for research, diagnosis and clinical assessment of treatment in idiopathic inflammatory myopathies.

Idiopathic inflammatory myopathies, known collectively as myositis, are chronic diseases that cause disability, mainly from muscle weakness, despite the use of immunosuppressive therapies. An improved outcome requires increased knowledge of the key molecular pathways that cause symptoms in muscles and other organs. Technological advances offer promise for improving our understanding of disease mechanisms, and some tools will be helpful in diagnosis and the assessment of therapeutic success. The application of new tools depends on their validation in longitudinal studies using clinical outcome measures combined with assessments of molecular events in affected organs. Clinical outcome measures and definitions of improvement have been developed and validated through the International Myositis Assessment and Clinical Studies collaboration. Some imaging techniques, such as MRI and magnetic resonance spectroscopy of muscles, and high-resolution CT of lungs, can assess changes in local inflammatory activity, among many other aspects of pathology. Changes in protein and gene expression patterns in repeated biopsies from affected organs (muscle, skin and lungs) provide molecular information and allow increasingly precise disease classifications and therapeutic evaluation, but are to date only research tools. This Review focuses on advances in diagnostic and outcome tools and their roles in clinical practice and clinical research in patients with polymyositis and dermatomyositis.