“This really holds the secret to the next generation of therapeutics,” said Dr. Joseph F. Arboleda-Velasquez, a cell biologist at Massachusetts Eye and Ear in Boston and a member of the research team. Dr. Arboleda-Velasquez is a co-founder of a biotechnology company looking to produce drugs that could act on this research.

A drug that delays the disease by two decades is not out of the question, said Dr. Diego Sepulveda-Falla, a neuropathologist at the University of Hamburg in Germany and a member of the research team. The mutation results in a potent version of a protein, Reelin, in the entorhinal cortex. That super-potent Reelin ultimately prevents tangled strands of tau proteins from sticking together and forming the structures that are a characteristic of Alzheimer’s.

The idea is to “go in with a syringe and treat only one area” of the brain, he said.

But that sort of treatment is off in the future and may not be possible, cautioned Dr. Thomas Bird, emeritus professor of neurology and clinical genetics at the University of Washington. Dr. Bird was not involved in the study.

The entorhinal cortex is a very small area. “We don’t know what sort of damage it might do, sticking needles in and dropping in chemicals,” he said.

Background: A new take from ongoing research.

The man with what the researchers are calling “resilience” to Alzheimer’s was part of a decades-long study of 6,000 people living in Colombia who have a gene mutation that causes Alzheimer’s in middle age. Many have agreed to genetic testing, brain scans and, after they die, brain autopsies.