Alzheimer disease and Down syndrome: factors in pathogenesis.

There is evidence to suggest that certain shared features exist in the pathogenesis of vascular disease and Alzheimer disease (AD) in the general population. In Down syndrome (DS) all adults over the age of 40 years develop sufficient neuropathology for a diagnosis of AD. However, vascular disease is not as common in DS as it is in the general population, particularly with respect to the development of atheromas. We discuss biological mechanisms and risk factors that may be common to both diseases including cholesterol metabolism, inflammation, plasminogen activator inhibitor and apolipoprotein E (Apo E). The study of individuals with DS may help to identify common pathogenic links as well as a disassociation between vascular disease and AD.