Early onset dementia (EOD) is conventionally defined by age of onset less than 65 years. It is increasingly recognized as a real public health problem because it reaches potentially active people. Although little studied, it is not uncommon and has some clinical and etiological features.

The aim of our study was to evaluate the prevalence of early onset dementia in psychiatric consultation to examinate sociodemographic, clinical and etiological characteristics of this entity.

It is a cross-sectional study in external consultation of the psychiatric hospital Razi. We collected the records of patients seen between 01/09/2011 and 01/09/2012 and in whom the diagnosis of dementia was retained as the diagnostic criteria of DSM IV.

We compared the epidemiological, clinical, and evolutionary dementia, beginning before the age of 65 with late onset dementia (LOD) (after 65 years).

50 patients were included. The prevalence of EOD was estimated at 20% of all dementias. There was an over representation of men in the early onset group. MMS average score of our patients was 16. This score did not differ between the two groups but differed significantly according to the etiological diagnosis. Alzheimer's disease was the main etiology for both groups. Compared to late-onset dementia, the EOD is characterized by greater heterogeneity in the etiologic diagnosis.

The EOD and the LOD seem to have common characteristics, but some features of the EOD especially etiological, emphasize the value of a more comprehensive approach to the research of curable dementia.