The following main histopathological features characterize MSA: α-synuclein-immunoreactive cellular inclusions, selective neuronal loss and axonal degeneration, myelin pallor with degeneration, microglial activation and astrogliosis (Trojanowski and Revesz 2007; Jellinger 2019a; Heras-Garvin and Stefanova 2020a). The gene discussed is SNCA; the disease is multiple system atrophy.