Psychiatrist and pathologist Alois Alzheimer first reported "a peculiar disease of the cerebral cortex" in 1906.1 His patient had died at age 55 years after nearly five years of progressive memory loss, language disability, and paranoia. Alzheimer described the neurofibrillary tangles and neuritic plaques that have since remained the anatomical hallmarks of what was originally thought to be a rare presenile dementia. A half century later, autopsy studies revealed that Alzheimer's disease (AD) was also the major cause of dementia in the elderly, accounting for at least half of all cases beginning after age 65. Alzheimer certainly could not foresee that he was describing an illness that today afflicts an estimated 1 to 2 million people in the United States.2
Stedman's Medical Dictionary3 defines a disease entity as having at least two of the following criteria: a recognized etiologic agent, an identifiable group of signs and symptoms,