Even though it is not the most common type of dementia, frontotemporal dementia (FTD) is a major health problem. It affects people younger than 65 with similar frequency as Alzheimer's dementia (AD) and has a progressive course that leads to inevitable deterioration in functioning. Still, FTD is not a unique entity in ICD- 10 classification.

To investigate the diagnostic and treatment difficulties in FTD.

To show very rapid and progressive deterioration in people with early onset FTD.

We will present a series of cases showing progressive cognitive deterioration and prominent personality changes in patients with FTD hospitalised at University Psychiatric Hospital Vrapce since 2013 to 2015. Collected data included anamnestic and heteroanamnestic information, blood tests and neroimaging.

Our findings showed a significance of early onset FTD, with subtle, untypical symptoms at the beginning, and galloping deterioration during the course of illness.

Presented patients with FTD showed rapid and progressive nature of disease with infaust prognosis. Even though early onset patients make 20% of overall number of patients with FTD, we consider that it is necessary to separate them from late onset patients in future classification systems.