The genetics of Alzheimer's disease

The genetics of Alzheimer's disease is produced by 3 essentially interactive gene groups: (1) APP and presenilin 1 and 2; (2) APOE E2, E3, and E4; (3) genes on chromosomes 9, 10, 12, etc. If any gene in (1) mutates, beta amyloid (Abeta) increases sharply beyond what the genes of (3) can remove, with early-onset Alzheimer's disease the result. With retention of Abeta by E4 in (2), Alzheimer's disease might result even though (1) and (3) are normal. If any gene in (3) mutates, the level of Abeta will rise, but because many genes are involved in Abeta removal, late-onset Alzheimer's disease would be detected only eventually.