The same gene mutations linked to inherited, early-onset Alzheimer’s disease have been found in people with the more common late-onset form of the illness.
The discovery by researchers at Washington University School of Medicine in St. Louis may lead doctors and researchers to change the way Alzheimer’s disease is classified.
They report their findings Feb. 1 in the online journal PLoS One (Public Library of Science).
“We probably shouldn’t think of early-onset disease as inherited and late-onset as sporadic because sporadic cases and familial clustering occur in both age groups,” says senior investigator Alison M. Goate, DPhil. “I think it’s reasonable to assume that at least some cases among both early- and late-onset disease have the same causes. Our findings suggest the disease mechanism can be the same, regardless of the age at which Alzheimer’s strikes. People who get the disease at younger ages probably have more risk factors and fewer protective ones, while those who develop the disease later in life may have more protective factors, but it appears the mechanism may be the same for both.”
The researchers used next-generation DNA sequencing to analyze genes linked to dementia. They sequenced the APP (amyloid precursor protein) gene, and the PSEN1 and PSEN2 (presenilin) genes. Mutations in those genes have been identified as causes of early-onset Alzheimer’s disease. They also sequenced the MAPT (microtubule associated protein tau) gene and GRN (progranulin) gene, which have been associated with inherited forms of another illness involving memory loss called frontotemporal dementia.
“Of those rare gene variants, we think about 5 percent likely contribute to Alzheimer’s disease,” says first author Carlos Cruchaga, PhD, assistant professor of psychiatry. “That may not seem like a lot, but so many people have the late-onset form of Alzheimer’s that even a very small percentage of patients with changes in these genes could represent very large numbers of affected individuals.”
For more from Jim Dryden of the WUSTL Newsroom, click here.
For a related story in US News & World Report, click here.