A total of 15 brain and 14 CSF samples with definite dementia with Lewy bodies (DLB, n = 6), Alzheimer ́s disease with amygdala Lewy body (AD/ALB, n = 3), and patients with concomitant Creutzfeldt-Jakob disease and Lewy body pathology (CJD/LBP, n = 6) comorbidity were tested for α-synuclein seeding activity using SAA assay utilizing recombinant α-synuclein (WT) with N-terminal His-tag. This evidence concerns the gene SNCA and Lewy body dementia.