When analysing the group of PM patients, S100A4 levels were associated only with extramuscular global assessment (β = 0.552; P = 0.002), while in the group of DM patients, S100A4 levels correlated with MYOACT (β = 0.557; P = 0.003) and CRP (β = 0.391; P = 0.029). Here, S100A4 is linked to polymyositis.