Idiopathic inflammatory myopathies: Improving diagnosis & disease management

Background: Approximately two-thirds of patients with idiopathic inflammatory myopathies (IIM) have a chronic/polyphasic disease course and suffer from residual disability, despite multimodality treatment. This clearly indicates the need for early and accurate diagnosis and better disease management. Methods: We performed narrative reviews and observational studies to explore potential for improvement in diagnosis by muscle imaging, muscle histopathology, cardiac screening, and serological profiling. We also conducted a phase-2 study on first-line intravenous immunoglobulin (IVIg). Results & conclusions: Autoantibody testing has become increasingly important in diagnosis, classification, and management of IIM. Even absence of autoantibodies may be significant. We found that patients with seronegative immune-mediated necrotising myopathy form a distinctive subgroup, amongst others characterised by frequent occurrence of extra-muscular disease activity. Both muscle ultrasound and magnetic resonance imaging were found to have the potential to play a role in diagnosing and monitoring disease activity in IIM patients. Histopathological examination of the fascia may have additional value in the early diagnosis of a subset of IIM patients. IIM patients should be routinely screened for (peri)myocarditis with high-sensitivity cardiac troponins and/or cardiac magnetic resonance imaging at time of diagnosis. First-line IVIg treatment for IIM patients is promising, but remains a “one size fits all” approach. Directions for future research: There is an urgent need of an algorithm for an accurate diagnosis, including concomitant extramuscular disease activity or cancer. Based on this, treatment in IIM patients should be customised, by adopting a more molecular approach to diagnosis and disease management, patient-centred outcomes. This requires international interdisciplinary collaboration in which all stakeholders are included.