Advances in the classification and management of idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies are a group of immune-mediated disorders characterised by multisystem involvement and a chronic disease course in two-thirds of adult patients. Autoantibodies can aid in the identification of disease subtypes and their associated severe complications, such as cancer or interstitial lung disease. Patients with idiopathic inflammatory myopathies need to be managed in a multidisciplinary setting. Treatment with intravenous immunoglobulins is efficacious in patients with refractory dermatomyositis, and can result in improvements in disease activity in the skin and muscle. Numerous randomised controlled trials are underway testing potential therapeutic agents that hold promise for the treatment of idiopathic inflammatory myopathies. Other advances include the identification of pathophysiological mechanisms. Induction of interferons in patients with dermatomyositis leads to the upregulation of interferon-stimulated genes in blood, skin, and muscle tissue. The interferon-induced transcripts could yield diagnostic biomarkers and biomarkers for monitoring disease activity. The identification of these potential biomarkers has also propelled the development of therapies targeting the interferon pathway—either upstream by using monoclonal autoantibodies or by blocking downstream signalling pathways via JAK inhibitors. A promising strategy for patients with refractory disease is targeting B cells with CD19-targeting chimeric antigen receptor T-cell therapy. Treatments targeting T cell lymphocytes and specific T-cell subsets are also under investigation.