PSEN1 and Cognitive impairment: In 2019, a homozygous APOE ε3 Christchurch allele was discovered in a Colombian woman carrying the PSEN1 E280A mutation, who instead of developing cognitive impairment at 44 years of age, presented with mild cognitive impairment in her late 70s and thus was protected from developing dementia for nearly 3 decades [32].