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What proportion of early familial Alzheimer disease cases are linked to the APP gene?
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Alzheimer disease
Histopathologic image of neuritic plaques in the cerebral cortex in a patient with Alzheimer disease of presenile onset (onset before age 65).
The APP gene, which is located on chromosome 21 and codes for amyloid precursor protein, is linked to only 2 to 3 percent of all early familial cases of Alzheimer disease.1
While defects in this gene are associated with the production and deposition of amyloid β-protein, they account for a very small percentage of early-onset cases compared to other genetic factors, such as mutations on chromosome 14, which are found in 70 to 80 percent of patients with early-onset disease.12