Clinical features of the behavioural variant of frontotemporal dementia that are useful for predicting underlying pathological subtypes of frontotemporal lobar degeneration.

BACKGROUND

The behavioural variant of frontotemporal dementia (bvFTD) is the most common phenotype of frontotemporal lobar degeneration (FTLD). FTLD is divided into three main pathological subtypes: tau-positive FTLD (FTLD-tau), FTLD-TAR DNA-binding protein (TDP), and FTLD-Fused in sarcoma (FUS). At present, it is difficult to predict the underlying pathological subtypes of sporadic bvFTD before a patient's death.

METHODS

We retrospectively investigated the clinical features of 34 Japanese patients with sporadic bvFTD, with or without motor neuron disease (MND), who had been pathologically diagnosed with FTLD. We examined whether, and how, the clinical features differed among Pick's disease, FTLD-TDP, and FTLD-FUS patients.

RESULTS

Six of the 34 patients developed MND during the course of bvFTD. These six bvFTD-MND patients were all pathologically diagnosed with FTLD-TDP. The other 28 patients were composed of 12 FTLD-tau patients including 11 Pick's disease patients, 8 FTLD-TDP patients, and 8 FTLD-FUS patients. A comparison of the clinical features of the three pathological subtypes of the 33 patients demonstrated that the age at onset was significantly younger in FTLD-FUS patients than in Pick's disease or FTLD-TDP patients. Furthermore, while hyperorality and dietary changes in the early stage of the disease were present in approximately 40% of Pick's disease and FTLD-FUS patients, they were absent in FTLD-TDP patients.

CONCLUSION

The comorbidity of MND, a younger age at onset, and hyperorality and dietary changes in the early stage may be useful clinical features for predicting underlying pathological subtypes of sporadic bvFTD. The results of our study should be confirmed by prospective studies employing a larger number of cases.