PSEN1 and Cognitive impairment: However, recent data showed that an old woman with presenilin 1 mutation (PSEN1-E280A) and APOE3 Christchurch mutation in homozygosis had only mild cognitive impairment in the presence of a high burden of β-amyloid in the brain, but a very low level of tau pathology when compared with other cases with this presenilin mutation [38].