The same protein that forms plaque in the brain in Alzheimer's disease, scientists say, also accumulates in the eyes of people with Down syndrome.
The new findings in Down syndrome show that the toxic protein, known as amyloid-_, that causes Alzheimer's pathology in the brain also leads to distinctive cataracts in the eyes.
The discovery is leading the researchers to develop an innovative eye test for early detection of Alzheimer's pathology in both disorders.
The study included investigators at the Brigham and Women's Hospital; Massachusetts Eye and Ear Infirmary; Massachusetts General Hospital; Harvard Medical School; Rush University Medical Center; Children's Hospital Boston, and the University of Washington, Seattle.
"People with Down syndrome develop symptoms of Alzheimer's-type dementia often by the age of 30," said Goldstein, senior co-author of the study.
"This is because they have an extra copy of a key Alzheimer's gene that leads to increased amyloid-_ accumulation in the brain. We discovered that this same protein starts to accumulate very early in the lens of the eye, even in children," Goldstein added.
Moncaster, co-lead author of the study, said: "The lens provides a window to the brain. The lens can't clear protein deposits the way the brain does. Our findings show that the same amyloid-_ protein that aggregates in the brain also accumulates in the lens and leads to these unusual cataracts in Down syndrome."
David G. Hunter, Ophthalmologist-in-Chief at Children's Hospital Boston and Vice Chairman of the Department of Ophthalmology at Harvard Medical School, said: "The results are striking. We have known that these cataracts are prevalent in people with Down syndrome and are sometimes seen at birth, but we never knew how they were related to the disorder-now we know. These distinctive cataracts appear only in people with advanced Alzheimer's disease and much earlier in Down syndrome."
Goldstein said: "We are developing an eye scanner to measure amyloid-_ in the lens. This approach may provide a way for early detection and monitoring of related pathology in the brain.
Effective treatments for the brain disease in Down syndrome and Alzheimer's disease are on the horizon, and early detection is the key for successful intervention. The path to effective treatment is what drives our research."