• Written informed consent obtained from participant and collateral source prior to any study-related procedures.

• Aged 18 (inclusive) or older and the child of an affected individual (clinically or by testing) in a pedigree with a known mutation for ADAD.

• Cognitively normal to very mild or mild cognitive impairment (CDR score range 0-1.0). Primary enrollment will focus on the recruitment of asymptomatic adult children who are more than 15 years younger than the estimated age of symptom onset. Enrollment of new participants with moderate cognitive impairment is allowed with the prior approval of the DIAN Coordinating Center.

• Has two persons who are not their full-blooded siblings who can serve as collateral sources for the study.

• Fluent in a language approved by the DIAN Coordinating Center at about the 6th grade level (international equivalent) or above.