Mutations in the presenilin 2 (PSEN2) gene are less commonly identified as genetic causes of early-onset familial Alzheimer's disease than mutations in the amyloid precursor protein (APP) and the presenilin 1 (PSEN1) genes. In fact, only 23 different mutations in the PSEN2 gene have been described in the literature. This paper deals with a sporadic case of a 55 year-old subject bearing an amino acid substitution from arginine to tryptophan at codon 71 of PSEN2 and presenting a peculiar early-onset Alzheimer's disease phenotype.