PSEN1 and Alzheimer disease: Although the search for such treatments continues, it is relevant to investigate variability in disease duration and to study factors influencing survival time.1 Autosomal dominant familial Alzheimer disease (ADAD) accounts for less than 1% of all AD cases.2 Pathogenic mutations in presenilin 1 (PSEN1),3 presenilin 2,4 or amyloid precursor protein (APP)5 are nearly 100% penetrant, and age at onset is correlated among family members.6 This offers a unique opportunity to study survival after symptom onset relatively precisely.