We conducted a retrospective analysis of data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) to examine the association between different α-Syn aggregation forms—Syn0 (no detectable α-Syn aggregates) and Syn1 (α-Syn aggregates detected, resembling those found in Parkinson's disease)—with the pathological and clinical features of AD. This evidence concerns the gene SYN1 and Alzheimer disease.