Alzheimer's: Woman With Extremely Rare Gene Mutation That Protects Her From Dementia Discovered

Scientists believe a woman with a high genetic risk of developing Alzheimer's in her 40s managed to escape the disease thanks to a rare gene mutation in her DNA.

The woman was part of a group of Colombian families likely to develop autosomal dominant Alzheimer's disease (ADAD), who researchers have been studying for the past two decades. These 1,200 individuals carry a mutation in their genes that can cause them to develop Alzheimer's in their forties. Most people develop the disease above the age of 65.

At the age of 70, the woman had developed what is known as mild cognitive impairment, where her thinking skills had waned—but not to a level warranting a dementia diagnosis.

She underwent tests that showed she had unusually high levels of amyloid beta in her brain. The build-up of this sticky protein in the brain is thought to contribute to the development of Alzheimer's disease. Scientists wanted to understand how she hadn't developed Alzheimer's, when not only did she have so much of the protein in her brain, but also carried the genetic mutation that put her at high risk of getting the disease.

Genetic tests revealed the woman had two copies of a rare variant on the APOE3 gene. The APOE gene tells the body how to make the apolipoprotein E protein, and APOE3 is one form, or allele.

Around 70 percent of people have the APOE3 allele, which doesn't affect a person's Alzheimer's risk, unlike APOE2 which is thought to protect against the condition, or APOE4 which is believed to worsen their chances.

Carrying the rare mutation might have prevented the tau protein, whose tangles are linked to Alzheimer's disease, from collecting in her brain, the researchers concluded.

Study co-author Eric M. Reiman, executive director of the Banner Alzheimer's Institute, told Newsweek the study suggests that APOE "has a greater impact on Alzheimer's than we thought," and could help with the development of therapies to treat and prevent the disorder by targeting the gene.

Reiman said promising APOE-silencing therapies and other methods for editing the gene "may be ready for testing in the next couple of years."

"We are working on experimental paradigms to put those drugs to the test when they are available in persons with one or two copies of the APOE4 gene, the major genetic risk factor for developing Alzheimer's at older ages," he said.

Yakeel T. Quiroz, a clinical neuropsychologist and neuroimaging researcher at Massachusetts General Hospital, who co-authored the study, told Newsweek he was shocked that the woman could "survive and thrive for so long when carrying a mutation" that put her at high risk of Alzheimer's.

Fiona Carragher, chief policy and research officer at the Alzheimer's Society charity, who did not work on the paper, told Newsweek: "This is a rare example where the study of just one person could change the thinking of a whole research field. This woman should have developed Alzheimer's in her 40s, but despite a really high number of amyloid plaques in her brain, she has reached 70 and is still living dementia free.

"The researchers identified a gene mutation that has protected against the brain cell damage that usually follows amyloid plaques, giving greater insight into the biological mechanisms at play in Alzheimer's disease."

Carragher continued: "This breakthrough opens up a new and promising avenue of Alzheimer's research, although further studies with larger numbers are needed.

"We need to understand more about how this protective gene mutation is working to make the brain more resilient to amyloid plaques, but the hope is that this exciting scientific advance could lead to new treatments and take us a step closer towards a cure for dementia."

Sara Imarisio, head of research at the charity Alzheimer's Research UK, told Newsweek: "Alzheimer's is a devastating disease of the brain and is caused by a complex mix of age, genetics and lifestyle. In rare inherited cases, faulty genes drive the development of the disease and overpower any protective factors. Understanding the role of rare protective genetic factors could be transformative in the development of new treatments.

"This study potentially indicates a new protective mechanism independent from amyloid build-up. Alzheimer's is a complex disease and this research highlights the need to explore every avenue in the search for better treatments."

She concluded: "As the findings from this study relate to a single individual, it will be critical to support these results with more evidence, but this case study provides a promising new direction for future research."