These include Parkinson’s disease (PD) and dementia with Lewy bodies (DLB) characterized by the presence of intraneuronal Lewy bodies (LB) and belonging together to the group of LB diseases, and multiple system atrophy (MSA), where α-synuclein accumulates in glial cytoplasmic inclusions (GCI). The gene discussed is SNCA; the disease is multiple system atrophy.