Role of Alpha-Synuclein in Frontotemporal Dementia: Narrative Review

BACKGROUND: Frontotemporal dementia (FTD) is traditionally classified based on the accumulation of either tau or TDP-43 proteins; however, the presence of alpha-synuclein (α-Syn) in these patients is increasingly recognized as a critical factor driving disease progression. METHODS: A comprehensive narrative review of recent clinical, neuropathological, and biochemical studies was conducted, focusing on cases of FTLD-synuclein and the occurrence of alpha-syn as a co-pathology in more common FTD variants. RESULTS: Current evidence indicates that α-syn often co-aggregates with tau and TDP-43 via "cross-seeding" mechanisms, significantly accelerating neuronal loss and contributing to clinical heterogeneity. Although FTLD-synuclein is a rare, distinct subtype that mimics atypical multiple system atrophy, secondary α-syn pathology is common and strongly correlates with rapid cognitive decline. Furthermore, existing diagnostic biomarkers typically fail to detect this pathological overlap, which may explain the limited efficacy in protein-specific clinical trials. CONCLUSIONS: α-Syn is a major, yet under-recognized, catalyst of neurodegeneration within the FTD spectrum. The findings emphasize the need for future therapeutic and diagnostic strategies to adopt multi-target approaches, addressing the synergistic toxicity of multiple protein aggregates rather than isolating single protein in isolation.