We selected a cohort of autopsy-confirmed Lewy body disease patients with hippocampal neuronal α-synuclein pathology and minimal age-related co-pathologies (<i>n</i>=62) and as a control for other intraneuronal hippocampal pathology, we used a cohort of cognitively healthy patients with focal hippocampal tau accumulation with minimal amyloid plaques, termed primary age-related tauopathy (<i>n</i>=12). The gene discussed is MAPT; the disease is Lewy body dementia.