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An American man with a rare Alzheimer’s gene mutation had a late onset of the disease — two decades later.
This is the second such case in the world. But the person is also a member of a family, of which 6,000 have the gene presenilin-1, or PSEN1, which is known to increase the risk of Alzheimer’s.
This discovery will improve understanding of the disease and help develop new treatments.
The study was published in the journal natural medicine, Based on the family history, the person should develop memory loss and other symptoms of Alzheimer’s in their 40s and 50s. However, due to a mutation in the gene PSEN1, he maintained full cognitive function until the age of 67.
The man eventually developed memory and thinking problems. At the age of 72, he was diagnosed with mild dementia, followed by further memory loss and an infection. He died of pneumonia at the age of 74.
The first such case was a woman from the same family, who lived with cognitive impairment until her 70s.
“The genetic variation we identified points to a pathway to greater resilience and prevention of Alzheimer’s disease symptoms,” said co-senior author Joseph Arboleda-Velásquez, an associate professor of ophthalmology at Massachusetts Eye and Ear.
“These are the kinds of insights we can’t get outside of patients. They’re showing us what’s important in terms of protection and challenging many of the field’s assumptions about Alzheimer’s disease and its development,” he said.
Insights from the team’s findings also point to a region of the brain that could provide a good therapeutic target.
Alzheimer’s disease is characterized primarily by amyloid plaques — sticky protein complexes — that kill neurons and cause dementia.
Some drugs recently approved by the US Food and Drug Administration also target these amyloid plaques. Although the drugs effectively remove amyloid from the brain, it leads to modest improvement in the rate of cognitive decline.
The study, however, challenged the theory, citing large amounts of amyloid plaques in the man’s brain.
Yadong Huang, a neurologist at the Gladstone Institute in San Francisco, California, said: “The fact that the person has a lot of amyloid plaques in their brain and remains healthy for a long time indicates that Alzheimer’s disease is complex.”
He suggests that there may be several types of Alzheimer’s, some of which are driven by amyloid.
“We need different ways to fight this disease in the end,” he said. It suggests that the association with tau plays a major role in mental decline. Several therapies targeting tau are currently in clinical trials.
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The above article was reprinted from The Wire with minor modifications to the title and text.