Making the diagnosis of mixed and non-Alzheimer's dementias.

Community pathologists are often called on to perform autopsies to confirm clinical diagnoses of Alzheimer's disease, by far the most common cause of dementia. Diagnostic criteria have been provided by the Consortium to Establish a Registry for Alzheimer's Disease. Beyond pure and simple Alzheimer's disease, a significant proportion of dementia brains will feature Alzheimer's disease mixed with Lewy bodies, historically associated with idiopathic Parkinson's disease, or combined with various manifestations of cerebrovascular disease. Less commonly, the pathologist will encounter Lewy body disease alone, pure cerebrovascular disease, Pick's disease, progressive supranuclear palsy, Creutzfeldt-Jakob disease, or dementia lacking distinctive histopathology. This article is intended to reacquaint pathologists with these disorders and to provide a practical step-by-step approach to making the diagnosis of these mixed and non-Alzheimer's dementias.