Mutations in the Presenilin 2 gene (PSEN2) represent the less frequent genetic cause of familial Alzheimer's disease (FAD). Only eight PSEN2 mutations, reported in approximately 27 families, satisfied strict criteria of pathogenicity. We reported a patient with early-onset FAD and the PSEN2 p.Met239Ile mutation, presenting with severe executive dysfunction and myoclonic tremor, associated with memory loss. Brain SPECT study showed an early hypoperfusion of the frontal cortex. We confirmed the pathogenicity of PSEN2 p.Met239Ile mutation and its heterogeneous phenotypic expression. The modulating effect of the Apolipoprotein E and Prion Protein gene polymorphisms on the phenotypic variability was not confirmed.