Alzheimer's disease and Down syndrome.

This report contains a summary of an extensive survey of autopsy data for mentally retarded persons. Among adults with DS, the brain neuropathology of AD was universal in those age 37 and over; claimed exceptions were indefensible. The behavioral evaluations of the DS adults, however, could be classified into three divisions: 1. "quiescent" (neither seizures nor dementia, 2). "partial" (seizures but no dementia), and 3). "active" (dementia +/- seizures). Thus, it is reasonable to argue that all persons with DS develop AD itself upon aging. However, DS cannot be used uncritically as an AD model since no increased incidence of active AD was found in DS with aging beyond the critical threshold age (mid-30's). Improved accurate quantification of Southern blots produced 100% accuracy in decoding blind samples of DS and non-DS samples. Using this system, DNA levels similar to those of DS have been demonstrated for all categories of AD at a small subsection of chromosome 21 near to, or within the DS DNA location on chromosome 21. Increased amounts of a complete, structural gene sequence were not found (or expected). The results provide evidence for a unitary hypothesis for DS and all forms of AD.