SNCA and Parkinson disease: The same group in a later study measured multiple forms of α-synuclein consisting of total α-synuclein, proteinase-K resistant α-synuclein, oxidized α-synuclein, and pS129 and demonstrated that the higher levels of total and proteinase K resistant α-synuclein and pS129 differentiated PD patients with motor symptoms (without dementia) from healthy controls with a high degree of accuracy (Abd-Elhadi et al., 2019).