||Parkinson disease may be the proto-type for the
alpha-synucleinopathies, but Alzheimer disease is in fact the most common
form. While it is diagnosed by the presence of plagues and tangles in a
demented individuals, over 50 percent of people with Alzheimer disease
also have Lewy bodies. The Lewy bodies is considered the characteristic
pathologic sign of Parkinson disease and contains abundant amount of alpha-synuclein.
In addition, there is a well-recognized Lewy-body variant of dementia, Lewy
bodies typically accumulate in Down syndrome, and they are common in
familial Alzheimer disease, as well.