To detect the expression of high‐mobility group box protein 1 (HMGB1) and toll‐like receptor 4 (TLR4) and their downstream signaling factors—myeloid differentiation factor 88 (MyD88), nuclear factor kappa B (NF‐κB), and tumor necrosis factor alpha (TNF‐α)—in the sera of patients with Parkinson's disease (PD) in order to evaluate the relationship of the HMGB1–TLR4 axis with PD development and progression. Here, TLR4 is linked to Parkinson disease.