PSEN1 and Alzheimer disease: In addition, the overlapping of clinical and neuropathologic features between AD and other neurodegenerative forms of dementia may result in misdiagnosis in 17–30% of AD cases [1,4,21], only two rare (25%) high-penetrant mutations in APP and PSEN1 were found in two EOAD patients, leaving 75% of the autosomal dominant pedigrees genetically unexplained in the cohort.