Although we could not obtain brain tissue from our patient, we could assume AD pathology in the patient's brain as he showed PS1‐S170F mutation, rapid cognitive decline, family history of early‐onset dementia and abnormal neuroimaging findings (cortical atrophy especially in the bilateral parietal areas and hypometabolism in the bilateral temporo‐parietal areas). This evidence concerns the gene PSEN1 and Alzheimer disease.