A lot of efforts have been done to unravel the genetics underlying early-onset Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD). However, still many familial early-onset dementia (EOD) cases show an unclear genetic background. The aim of this study was to evaluate the role of the known causative mutations and possible pathogenic variants associated with AD and FTLD in a Finnish EOD cohort. The cohort consisted of 39 patients (mean age at onset 54.8 years, range 39-65) with a positive family history of dementia or an atypical or rapidly progressive course of the disease. None of the patients carried the C9orf72 hexanucleotide repeat expansion. Mutations and variants in APP,

Background: Frontotemporal lobar degeneration (FTLD) is responsible for as many as every fifth case of early-onset dementia. Very few epidemiological studies of FTLD have been conducted; there are no published epidemiological data of FTLD from Finland or the other Nordic countries. The C9ORF72 expansion-associated FTLD is common in Finland; thus, the prevalence of FTLD is expected to be high in this population. Methods: We retrospectively evaluated the incidence and prevalence of FTLD in university hospital settings in Northern Finland. Results: The mean 1-year incidence of FTLD was 5.54/100,000 (range 1.9-11.3/100,000) in the population aged 45-65 years. The prevalence of FTLD in the same age group was 20.5/100,000. Conclusion: The incidence and prevalence of FTLD in Finland seem to be the highest in Europe. However, studies from different countries may not be directly mutually comparable due to methodological issues.

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