This ultra rare mutation appears to help stave off the disease by minimizing the binding of a particular sugar compound to an important gene. That finding suggests that treatments could be developed to give other people that same protective mechanism.

“I’m very excited to see this new study come out — the impact is dramatic,” said Dr. Yadong Huang, a senior investigator at Gladstone Institutes, who was not involved in the research. “For both research and therapeutic development, this new finding is very important.”

A drug or gene therapy would not be available any time soon because scientists first need to replicate the protective mechanism found in this one patient by testing it in laboratory animals and human brain cells.

Still, this case comes at a time when the Alzheimer’s field is craving new approaches after billions of dollars have been spent on developing and testing treatments and some 200 drug trials have failed. It has been more than 15 years since the last treatment for dementia was approved, and the few drugs available do not work very well for very long.

[Like the Science Times page on Facebook. | Sign up for the Science Times newsletter.]

The woman is entering her late 70s now and lives in Medellín, the epicenter for the world’s largest family to experience Alzheimer’s. It is an extended Colombian family of about 6,000 people whose members have been plagued with dementia for centuries, a condition they called “La Bobera” — “the foolishness” — and attributed to superstitious causes.