Considering that PD and MSA have different structures of accumulated α-synuclein (Klingstedt et al., 2019; Lau et al., 2020; Prusiner et al., 2015; Schweighauser et al., 2020; Shahnawaz et al., 2020; Woerman et al., 2019; Woerman et al., 2015), it seems highly likely that the structures of α-synuclein fibrils determine the lesions observed in these diseases. The gene discussed is SNCA; the disease is Parkinson disease.