Frontotemporal lobar degeneration and ubiquitin immunohistochemistry.

We set out to determine the frequency of the different pathologies underlying frontotemporal degeneration (FTD) in our brain bank series, by reviewing all cases of pathologically diagnosed FTD over the last 12 years. We identified and reviewed 29 cases of FTD and classified them using the most recent consensus criteria with further histological analysis of 6 initially unclassifiable cases. Detailed histological analysis of these 6 cases revealed variable numbers of ubiquitin-positive (tau and alpha-synuclein-negative) inclusions in 5 cases, consistent with the diagnosis of frontotemporal lobar degeneration with ubiquitin-only-immunoreactive neuronal changes (FTLD-U). As a consequence of the current re-evaluation, 18 (62%) of the 29 cases with FTD have underlying pathology consistent with FTLD-U. Therefore in our brain bank series of frontotemporal degeneration, most cases were non-tauopathies with FTLD-U accounting for 62% of all the diagnoses.