Frontotemporal dementia mimicking dementia with Lewy bodies

Some patients with frontotemporal dementia (FTD) have concomitant extrapyramidal symptoms and psychosis and may simultaneously meet consensus criteria for FTD and for dementia with Lewy bodies (DLB). Clinicopathologic studies are helpful in understanding the underlying neurodegenerative process in such cases.

To describe clinical and pathologic features of 6 patients with signs and symptoms suggestive of both a diagnosis of FTD and DLB at first clinical presentation, of which 2 patients have now undergone autopsy, and to compare them with autopsy-confirmed FTD and Lewy body disease patients.

All 6 patients met published consensus criteria for a diagnosis of both FTD and DLB (5 probable and 1 possible). Clinical symptoms of FTD included personality and behavioral changes, whereas those suggestive of DLB included Parkinsonism, fluctuating cognition, parasomnia, and hallucinations. Five patients underwent single photon emission computed tomography ((99m)Tc) imaging, which showed varying degrees of frontal lobe hypoperfusion. Magnetic resonance imaging, electroencephalogram, and electromyogram were not helpful in differentiating FTD from DLB. Histologic examination of the 2 autopsy cases was consistent with a pathologic diagnosis of TDP-43 proteinopathy; specifically frontotemporal lobar degeneration with ubiquitin-only immunoreactive changes, type 1. There were significant differences between these 6 patients and the 2 groups of autopsy confirmed FTD and Lewy body disease patients.

We have identified a novel group of FTD patients with clinical features that overlap with DLB, yet seem to be different from both typical FTD and typical Lewy body disease.