Abstract
Presenilin 1 (PS1) mutations are the most common cause of early-onset familial Alzheimer's disease (EOFAD). They show a common phenotypic profile characterized by early age of onset, severe dementia and distinct neurodegeneration. The largest population of EOFAD carries the E280A mutation in PS1 and resides in Antioquia, Colombia, currently comprising around 5,000 individuals. Carriers start showing memory impairment in the third decade of life, followed by progressive impairment of language and other cognitive processes. They reach mild cognitive impairment around 45 and dementia around 50 years of age. There is some phenotypic variability among the carriers of this single PS1 mutation. Some patients present with epilepsy, verbal impairment, and cerebellar ataxia. Neuropathologically, PS1 E280A cases show pronounced brain atrophy, severe amyloid-β pathology, distinct hyperphosphorylated tau-related pathology, and cerebellar damage. The earliest event identified by functional magnetic imaging resonance is hyperactivation within the right anterior hippocampus around 33 years of age. This well-studied population with a clear pre-clinical profile and wide phenotypic variability in age of onset and clinical presentation is ideally suited for clinical trials and to study molecular mechanisms of Alzheimer's disease.