Amyloid plaques—protein clumps that are one of the hallmarks of Alzheimer’s disease—occur at roughly the same level in the brains of people with Down syndrome who have Alzheimer’s as they do in people with forms of hereditary, early-onset Alzheimer’s, according to research funded by the National Institutes of Health. Based on the largest study of its kind to date, the findings suggest that individuals with Alzheimer’s and Down syndrome may benefit from participating in studies on Alzheimer’s therapies aimed at slowing formation of amyloid plaques.