The Chinese Familial Alzheimer's Network

Familial Alzheimer's disease group Inclusion criteria:

1. Written informed consent obtained from the participant or a legal guardian prior toany study-related procedures;
2. At least two first-degree relatives in a family have AD (clinically or by testing)，andat least 3 out of 2 generations are patients;
3. At least one family member with normal cognitive function (the age should be greaterthan the average age of onset of the family);
4. Pedigrees carrying FAD pathogenic genes (APP/PSEN1/PSEN2);
5. People in this family >18 years old can be recruited;
6. Participant is cognitively normal or demented but not reaching bedridden level;
7. Participants are able to provide two reliable informants who can provide clinicalinformation;
8. Dementia is diagnosed according to the criteria described by the Diagnostic andStatistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-R );
9. The diagnosis of AD is made using the National Institute of Neurologic andCommunicative Disorders and Stroke and the Alzheimer's Disease and Related DisordersAssociation (NINCDS-ADRDA ) or National Institute on Aging and the Alzheimer'sAssociation (NIA-AA) criteria ;
10. The diagnosis of MCI is made according to Petersen criteria and the classification isaccording to the method of Lopez et al.

Exclusion criteria:

1. Dementia caused by other factors such as depression, other psychiatric illnesses,thyroid dysfunction, encephalitis, multiple sclerosis, brain trauma, brain tumor,syphilis, acquired immunodeficiency syndrome (AIDS), Creutzfeldt-Jakob disease andother types of dementias such as vascular dementia (VaD), frontotemporal dementia (FTD), dementia with Lewy bodies (DLB), and Parkinson's dementia (PDD)；
2. MRI and laboratory tests do not support or rule out a diagnosis of AD；
3. Severe circulatory, respiratory, urinary, digestive, hematopoietic diseases (such asunstable angina, uncontrollable asthma, active gastric bleeding) and cancer；
4. Participant has severe psychiatric illness or severe dementia that would interfere incompleting initial and follow-up clinical assessments；
5. Participant has a history of alcoholism or drug abuse；
6. Pregnant or lactating women；
7. No reliable informant；
8. Lumbar puncture exclusion criteria：coagulation disorders or platelet counts < 100,000cells/μL, lumbar surgery within the last 6 months prior to lumbar puncture thatinterferes with anatomy of the inter-vertebral spaces, History of chronic or repeatedCSF leakage following previous LP(s);
9. MRI Exclusion Criteria: electronic and magnetic metal implants such as pacemakers,artificial heart valve, metal prosthesis, metal joint, etc.; metallic foreign body inthe eye; aneurysm clips in the brain. Normal control group Inclusion criteria:
10. Aged 18 (inclusive) or above;
11. Normal MMSE and MoCA evaluations. MMSE>19 points for illiteracy, >24 points for thoseeducated less than 7 years, >27 points for those educated equal to or more than 7years. MoCA>13 points for illiteracy, >19 points for those educated less than 7 years, >24 points for those educated equal to or more than 7 years. Exclusion criteria:
12. Subjects with abnormal MMSE or MoCA scores;
13. Subjects with a history of cerebral infarction, traumatic brain injury or relatedmanifestations in MRI;
14. Other neurological diseases that can cause brain dysfunction (such as depression,brain tumor, Parkinson's disease, metabolic encephalopathy, encephalitis, multiplesclerosis, epilepsy, brain trauma, normal intracranial pressure hydrocephalus, etc.);
15. Other systemic diseases that can cause cognitive impairment (such as liver, renal andthyroid insufficiency, severe anemia, folic acid or vitamin B12 deficiency, syphilis,HIV infection, alcohol and drug abuse, etc.);
16. Mental and neurodevelopmental retardation;
17. Suffering from a disease that cannot be combined with a cognitive examination;
18. Contraindications to MRI;
19. Refuse to draw blood;
20. Refuse to sign the informed consent at baseline.