HMGB1 and Parkinson disease: The serum HMGB1 levels of the patients with PD at Stages I, II, III, and IV were 3.53 ± 1.01, 6.41 ± 0.87, 7.16 ± 0.68, and 8.44 ± 1.12, respectively, which were significantly higher than those of the healthy volunteers (p < .05).