S100A9 and Parkinson disease: S100A9 amyloids were found to colocalise with amyloid-β peptide plaques in patients with AD and mild-cognitive impairment [4,8], with α-synuclein in Lewy bodies in patients with Parkinson’s disease [5], and form precursor plaques and amyloid aggregates in the cells and tissues after traumatic brain injury as a precursor state for AD [9].