[Alzheimer's disease: variety without unity].

The diagnosis of Alzheimer's Disease is quite common these days. Nonetheless, a clearcut definition of the concept of Alzheimer's Disease is still beyond scientific reach. This discrepancy makes it particularly relevant to explore the meanings of the concept, and to ask some questions concerning how diseases are defined. Alzheimer's Disease has been introduced into nosology by Kraepelin, at the beginning of the 20th century. Kraepelin's claim that Alzheimer's Disease is a disease sui generis, was contested promptly: by Alzheimer himself, for instance. This initiated a history of intensive debate concerning the distinction between Alzheimer's Disease and Senile Dementia on the one hand, and the distinction between Senile Dementia and ageing on the other. During the 1970s and 1980s, several important changes took place, which elucidated the use of clinical and neuropathological criteria for the diagnosis of dementia and Alzheimer's Disease. This, however, did not end the debate. A definite criterion--a gold standard--for the diagnosis of Alzheimer's Disease is still lacking. Recent developments in the field of molecular biology furthered the insights into the pathological processes in Alzheimer's Disease. These developments show that a unitary definition of Alzheimer's Disease (including the presenile and senile forms) is not to be expected. There are therefore insufficient reasons to accept a disease entity called 'Alzheimer's Disease'. In this sense we are not far removed from Alzheimer's and Kraepelin's days. The interpretation--both in- and outside science--of Alzheimer's Disease as an entity is therefore not supported by sound scientific arguments.(ABSTRACT TRUNCATED AT 250 WORDS)