Cross-sectional analysis of 61 patients reveals that Parkinson's disease dementia (PDD) produces more severe motor dysfunction, psychotic symptoms, and autonomic impairment compared to dementia with Lewy bodies (DLB), despite both conditions involving alpha-synuclein protein aggregation. The research identified divergent neuropsychiatric symptom clustering patterns between the two synucleinopathies. These findings challenge the prevailing clinical assumption that PDD and DLB represent merely different temporal presentations of the same underlying pathology. The distinct symptom networks suggest different neurobiological mechanisms may drive each condition's progression. For PDD patients, depression interconnects with delusions, apathy, and behavioral disinhibition, indicating limbic-frontal circuit involvement. In contrast, DLB patients show depression linking primarily to hallucinations, suggesting occipital-temporal pathway disruption. This differential patterning has immediate clinical relevance for personalized treatment approaches. Clinicians managing PDD should prioritize comprehensive psychiatric screening given the complex symptom interactions, while DLB management might focus more on perceptual disturbances. However, the study's modest sample size and cross-sectional design limit definitive conclusions about causality. Longitudinal studies tracking symptom evolution could better illuminate whether these represent distinct disease trajectories or severity-dependent manifestations of shared pathophysiology.