The development and validation of measures of disease activity, damage, and health-related quality of life (HRQOL) over the past 30 years has been fundamental in advancing research and care for patients with adult and juvenile idiopathic inflammatory myopathies (IIMs).1These efforts have resulted in the development of core set measures of disease activity and damage for myositis, and the American College of Rheumatology (ACR)/European Alliance of Associations for Rheumatology (EULAR)–endorsed Myositis Response Criteria, which have been successfully implemented in IIM clinical trials and which recently facilitated the US Food and Drug Administration licensure of intravenous immunoglobulin for dermatomyositis (DM).2-5