Dominantly inherited Alzheimer's disease represents less than 1% of all cases of Alzheimer's. It is an important model for study because the responsible mutations have known biochemical consequences that are believed to underlie the pathological basis of the disorder.

Three major hypotheses will be tested:

• There is a period of preclinical (presymptomatic) Alzheimer's disease in individuals who are destined to develop early-onset dementia (gene carriers) that can be detected by changes in biological fluids and in neuroimaging results compared with individuals who will not develop early-onset dementia (noncarriers).
• Because all identified causative mutations for Alzheimer's disease affect the normal processing of amyloid precursor protein (APP) and increase brain levels of amyloid-beta 42 (Aβ42), the sequence of preclinical changes initially will involve Aβ42 production and clearance and reduced levels in cerebrospinal fluid, followed by evidence for cerebral deposition of Aβ42 (amyloid imaging), followed by cerebral metabolic activity (functional imaging), and finally by regional atrophy (structural imaging).
• The phenotype of symptomatic early-onset familial Alzheimer's, including its clinical course, is similar to that of late-onset "sporadic" Alzheimer's.

The following specific aims will be used to test these hypotheses:

1. Establish an international, multicenter registry of individuals (mutation carriers and noncarriers; presymptomatic and symptomatic) who are biological adult children of a parent with a known causative mutation for Alzheimer's disease in the APP, PSEN1, or PSEN2 genes.
2. In presymptomatic individuals, compare mutation carriers and noncarriers to determine the order in which changes in clinical, cognitive, neuroimaging, and biomarker indicators of Alzheimer's disease occur prior to dementia.
3. In symptomatic individuals, compare the clinical and neuropathological phenotypes of autosomal dominant Alzheimer's to those of late-onset "sporadic" Alzheimer's.
4. Maintain the DIAN Central Archive, an integrated database incorporating all information obtained from individuals in the registry, to permit analyses among the various data domains and to disseminate the data to qualified investigators.
5. All DIAN participants who wish to know their mutation status will have the costs of genetic counseling and clinical mutation testing paid for by the grant. The clinical genetic counseling and testing are provided as an optional participant benefit and are not part of the DIAN research design.