Presymptomatic Genetic Testing with an APP Mutation in Early-Onset Alzheimer Disease: A Descriptive Study of Sibship Dynamics.

Early-onset Alzheimer disease (AD) accounts for only 5% of all cases of Alzheimer disease. To date, mutations in three different genes, the Amyloid precursor protein (APP), Presenilin 1 (PS1), and Presenilin 2 (PS2), have been identified as causative in early-onset AD, making predictive testing possible. Predictive testing for early-onset Alzheimer disease is a relatively new phenomenon. This paper describes the process of identifying a new mutation in the APP gene associated with early-onset AD, notifying family members, and offering participation in research as well as predictive testing. The goal is to share the complexities of predictive testing in a sibship newly identified as being at risk for an adult-onset, incurable neurodegenerative disease.