A few studies have reported the presence rare benign polymorphisms of PSEN-1 gene in patients with FTLD.[57] One study reported two novel PSEN-1 mutations in two patients, one with a clinical diagnosis of FTD but with neuropathological diagnosis of AD and another one in AD with frontal lobe signs, recommending screening for mutations in PSEN-1 in familial FTLD cases without mutations in the known relevant genes. This evidence concerns the gene PSEN1 and Alzheimer disease.