ABSTRACT
Functional deterioration in adults with Down syndrome (DS) has been noted since the nineteenth century. In 1876, J. Fraser and A. Mitchel wrote that individuals with DS had a 'sort of precipitated senility.' One of the seminal observations of recent history has been the detection of Alzheimer’s disease (AD) neuropathology in the brains of adults with DS who are older than 35 years. One needs to critically examine adults with DS who present with functional decline, in order to avoid mistakenly assuming that all decline in dementia is due to dementia in Alzheimer's disease (DAD), and to take a cautious approach to the clinical work-up of dementia in DS. A decline in functioning in an adult with DS does not automatically mean that DAD is present. The goal of the clinical evaluation of DAD in individuals with DS has not changed since clinicians first pondered the aetiology of functional decline.
