Lewy body disease (LBD) is one of the most common neurodegenerative diseases and second only to Alzheimer's disease in terms of prevalence, disability, and societal/financial burden. The phenotypic variability of LBD is striking, as it can manifest as the well-known disorder of Parkinson's disease without (PD) and with dementia (PDD), as well as DLB, MCI, REM sleep behavior disorder (RBD), pure autonomic failure (PAF), and other syndromes.