Youngest Alzheimer's Patient Ever?

How old do you have to be to get Alzheimer's?  Well, we know that, with young onset (or familial) Alzheimer's, there are cases of people in their 30s, with one case of someone diagnosed as young as 21 years of age.  As we discussed in Beating the Dementia Monster, familial Alzheimer's is caused by any of three specific genes, and if you have one of those genes you'll almost surely develop plaques, tangles, and dementia.  Fortunately, these genes are relatively rare.  There may only be 300 or so families in the world carrying them.  But, as with one family in Columbia, people who develop familial Alzheimer's disease provide a rich basis for study.  People who will develop this form of the disease in the future are easy to identify through genetic testing, and they are more likely to be free of other diseases that afflict older people.  The presence of these other diseases confounds studies of people with Alzheimer's.

But how young can someone be and still develop old onset (or sporadic) Alzheimer's?  This type may or may not have a genetic marker, like the APOE4 gene they test you for at 23andMe, and it's relatively unknown below the age of 65.

Research published in The Journal of Alzheimer's Disease examined the case of a young Chinese man of just 19 years of age who, by all available evidence, suffered from sporadic Alzheimer's disease.  He was still living at the time the research was published, and so there was not yet an autopsy to look for plaques and tangles in his brain.  However, the available biomarkers all ruled out other potential causes of his dementia.  As with me, he had significant atrophy of his hippocampus, and tests of his cerebrospinal fluid were typical for Alzheimer's.  

The young man began to experience problems with memory and cognition when he was 17 and progressed from there.  Neuropsychological tests found him impaired in memory and cognition.  When his case was evaluated, he had no family history of Alzheimer's, and he had no genetic markers for the disease -- the genes for familial Alzheimer's and those that might predict sporadic Alzheimer's.

So is this one of those weird things that just happens?  Some people (wisely) don't think so.  The more we learn about the disease, the more we discover that we don't know.  The authors of the research suggested that studying this case, and perhaps looking for others, might provide important new insights on how and why Alzheimer's develops.