Professor Dennis Selkoe discusses the age at which plaque-forming a-beta can begin to build up. Children with Down syndrome may have these plaques, otherwise childhood instances are rare.

It’s a wonderful question to ask, how early in life a-beta [amyloid beta] can build up. The only situation that I am aware of, two situations in which it builds up very early are the condition called Down syndrome, or trisomy 21, and very rare cases of familial Alzheimer’s disease due to a mutation in a gene called presenilin, one of the genes that makes a-beta. But those look like an Alzheimer’s [disease] picture from the beginning. If a patient with Down syndrome dies at age 12 of a car accident or of some other complication of Down syndrome, one will already see telltale plaques of a-beta in the brain, so it’s an Alzheimer’s-like picture that begins very early. If a child has an abnormality of the entorhinal cortex and its connectivity, from one part of the entorhinal cortex to another part of the hippocampus, that in itself won’t predict Alzheimer’s disease. It’s only these two conditions we know of that could already predispose people to Alzheimer’s [disease] as early as childhood: Down syndrome and a rare familial form of Alzheimer’s [disease] in which the problem is too much a-beta production. Many other conditions in the brain in childhood or during development that can lead to impaired cognition or can even predispose a person to another kind of dementia, not Alzheimer’s [disease] – those do not relate to amyloid beta protein. Just these two conditions: Down [syndrome] and rare forms of early-onset familial Alzheimer’s [disease] relate to a-beta early in life.

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