PSEN1 and early-onset autosomal dominant Alzheimer disease: A similar finding of resilience was noted in a recent study45 that describes an individual who was homozygous for a rare protective variant in the APOE-ε3 allele (Christchurch mutation), which is thought to explain the resilience against the effect of a mutation in the presenilin 1 gene, which is associated with autosomal dominant early-onset Alzheimer disease.