HMGB1 and dermatomyositis: Significantly higher serum levels of HMGB1 were found in patients with PM [12.75 ng/ml (4.34–25.07 ng/ml), p < 0.001] and DM [20.75 ng/ml (3.80–124.88 ng/ml), p < 0.001] than in healthy controls [5.64 ng/ml (2.71–8.71 ng/ml)].