Myositis specific antibodies to predict treatment response in idiopathic inflammatory myopathies

Recent study findings, published in Arthritis Care & Research, have shown that patients with dermatomyositis-specific autoantibodies achieved better levels of treatment response compared to other autoantibody-defined groups upon evaluation of subjects with idiopathic inflammatory myopathies. The researchers also noted that dysphagia, a shorter time span from symptom onset to diagnosis, and intensive initial immunosuppressive treatment were associated with a higher therapeutic response rate after 1 year of pharmacologic treatment, irrespective of the autoantibody status. The registry-based study was intended to identify prospective autoantibodies that can act as predictors of response to immunosuppressive drugs in patients with idiopathic inflammatory myopathies.

Fabricio Espinosa-Ortega and co-researchers from the Karolinska Institute, Stockholm Sweden, collected the data of 156 patients with idiopathic inflammatory myopathies from the Swedish national registry, which included 40% patients with dermatomyositis, 5% with an amyopathic form of dermatomyositis, and the remaining 55% with polymyositis. Nearly 90% of the patients were treated with glucocorticoids at baseline and 78% of patients received additional immunosuppressive drugs within the first year.

The altogether median improvement score noted after 1 year of treatment was 27.5 (interquartile range 10–51). Out of 156 patients, the minimal response was achieved by 96 patients, 60 patients attained moderate response, and major response by 19 patients. The patients with the presence of dermatomyositis-specific autoantibodies had a greater number of achieving a moderate response compared to other groups. The odds of achieving moderate response to treatment in patients with dermatomyositis-specific autoantibodies was odds ratio 4.12 (95% confidence interval 1.2–16.5) when compared to patients without the auto-antibodies.

The present study highlights the benefits of identifying autoantibodies groups with early idiopathic inflammatory myopathies and the significance of early initiation of immunosuppressive therapy post-diagnosis for higher clinical response rate, irrespective of the autoantibody status.

Reference: Espinosa-Ortega F, Holmqvist M, Dastmalchi M, Lundberg IE, Alexanderson H. Factors Associated With Treatment Response in Patients With Idiopathic Inflammatory Myopathies: A Registry-Based Study. Arthritis Care Res (Hoboken). 2022;74(3):468-477.