For a study, it was determined that idiopathic inflammatory myopathies (IIMs) were a diverse set of illnesses with a paucity of high-quality knowledge on how to treat them. As a result, researchers set out to investigate the prevalent treatment procedures. Drug usage patterns, predictors, drug retention rates, effectiveness, and adverse drug responses were examined in adults and children newly diagnosed with IIM (2017–2020) and prospectively monitored and compared with real-world data through a medical records review. Dermatomyositis (41% adults, 93% children) was the most prevalent subtype among the 181 adults (male-to-female ratio, 1:4.6) and 30 children (M: F, 1.3:1). Methotrexate (MTX) was the most often used medicine (67% in adults and 90% in children), followed by azathioprine (AZA) and mycophenolate mofetil (MMF). 

For patients with the antisynthetase syndrome (ASSD) and lung involvement, MMF, AZA, cyclophosphamide, and rituximab (RTX) were favored, whereas MTX was avoided. Drug preferences were unaffected by functional class or family wealth. In overlap myositis, glucocorticoids were started at a lower dose (45% vs 80%, P= 0.001), and the period to obtain the lowest dose of glucocorticoids was greater than 24 months (77% vs 14%, P= 0.002). Over a median of 35 months, RTX had the highest overall retention rate (75%), followed by MTX (58%). RTX had the greatest relapse-free survival rate, followed by MTX. The most prevalent causes for cessation were adverse medication responses with MTX and MMF, ineffectiveness with AZA, and RTX expense.

MTX was the most chosen medicine in both adults and children in this first study of drug usage and retention in IIM patients, with the exception of those with ASSD or lung illness. The involvement of organs and the subtype of IIM were important predictors of medication choice. Overall, RTX and MTX had strong retention rates, followed by AZA and MMF.