Rapidly progressive Fronto-temporal dementia (FTD) associated with Frontotemporal lobar degeneration (FTLD) in the presence of Fused in Sarcoma (FUS) protein: a rare, sporadic, and aggressive form of FTD.

Fronto-temporal dementia (FTD) associated with Fused in Sarcoma (FUS) protein accumulation is an uncommon cause of FTD with a distinct syndrome of young age onset behavioral variant FTD, without a family history of FTD and caudate atrophy. We present a sporadic case of a 61-year-old patient with mixed features of both behavioral variant FTD with later semantic language dissolution associated with pathologically proven FUS. He was older than usual for FUS pathology, his course was rapidly progressive, and he had atypical language features. This case broadens the clinical spectrum caused by FUS-protein-related FTD.