Negative neurofilament light and tau immunostaining in frontotemporal dementia.

We investigated the immunohistochemical stainability of phosphorylated tau and the light (NFL), intermediate (NFM), and heavy (NFH) neurofilament proteins in postmortem brain tissue from 8 patients with frontotemporal dementia (FTD), for comparison with 6 patients with Alzheimer's disease (AD), and 6 normal controls. In the FTD group, the neuropathological diagnosis was pure frontal-lobe degeneration of non-Alzheimer type (FLD) in 6 cases and in the remaining 2 cases mixed FLD-AD and frontal AD, respectively. The staining for tau was negative in 5 of the FLD cases and faintly positive in 1, but positive in all AD cases. The antibodies against NFM and NFH stained positive in FLD, AD, and controls, whereas the staining for NFL was negative in all FLD cases and positive in 1 AD case and in the controls. These findings regarding NFL and tau staining may be useful in the differential diagnosis of FLD and AD.