The Genetic Characterization of Dementia

Background: \- Researchers are interested in learning more about dementia and its causes. They want to look at the genetic basis of dementia. Identifying genetic aspects of dementia may help provide better tests and treatments for it. It may also show rare gene variants that can cause or alter a person's risks for developing dementia. This study will look at people who have dementia, their family members, and healthy volunteers. Objectives: \- To study genetic influences on dementia. Eligibility: * Individuals who have been diagnosed with dementia. * Family members of individuals who have been diagnosed with dementia. * Healthy volunteers at least 18 years of age. Design: * Participants will be interviewed and answer questions about their medical history. They will also provide general information on the relatives' medical histories. * Participants will provide a blood sample for genetic testing. * Participants will remain on the study for up to 10 years. They will have regular visits to monitor their brain health and function. * Treatment will not be provided as part of this study.