Serum interleukin-17A level is associated with disease activity of adult patients with dermatomyositis and polymyositis.

To assess serum interleukin (IL)-17A levels in patients with dermatomyositis (DM) and polymyositis (PM) and correlate them with the demographic, clinical, laboratory and therapeutic data of these diseases.This was a cross-sectional, single-centre study that included defined DM and PM patients who were age-, gender- and ethnicity-matched to healthy individuals. Serum IL-17A analysis, as well as analysis for other cytokines (IL-6, TNFα and IFNγ), was performed by multiplex immunoassay. The disease status parameters were based on the International Myositis Assessment and Clinical Studies Group (IMACS) set scores.Eighty DM, 32 PM patients and 104 healthy individuals were enrolled. Mean age of patients with DM and PM was 46.0 and 47.7, respectively, with a predominance of women and white ethnicity in both groups. Overall, clinical, laboratory, therapeutic, and current disease status were similar among patients with DM and PM. Median serum IL-17A level was higher in patients with PM and DM than the control group (0.73 vs. 0.49 vs. 0.35 pg/mL, respectively; p<0.050) and higher in PM when compared to DM (p<0.001). In DM, serum IL-17A levels were associated with cumulative cutaneous lesions, IMACS parameters, and serum IL-6 and IFNγ levels. In PM, serum IL-17A levels correlated with patients' current age, IMACS parameters and serum TNFα and IFNγ levels.Serum IL-17A levels are not only increased, but also associated with disease activity in patients with DM and PM. Our data strongly suggest that IL-17A may be a biomarker of disease activity for these systemic autoimmune myopathies.