When There's No Amyloid, It’s Not Alzheimer’s

This is the heading to a fascinating article in the latest Alzforum weekly newsletter. Here's a link to the article:

http://www.alzforum.org/news/research-news/when-theres-no-amyloid-its-not-alzheimers?utm_source=Alzforum+Weekly+Newsletter&utm_campaign=0372e368ea-September_14_2015_Newsletter&utm_medium=email&utm_term=0_944a562dd7-0372e368ea-91738709

And the first paragraph gives you the gist:

Reporting in the August 24 JAMA Neurology online, researchers led by Eric Reiman at Banner Health in Phoenix, confirm what others have suspected from PET imaging, namely, that as many as one-third of the people clinically diagnosed with mild to moderate Alzheimer's disease do not meet criteria for significant amyloid accumulation in the cerebral cortex. Reiman and colleagues came to this conclusion after examining brain tissue postmortem—the gold standard for assessing amyloid burden. The finding puts the kibosh on the idea that some PET scans are negative because amyloid ligands bind poorly to particular forms of amyloid in some AD patients. It also reinforces questions about the accuracy of clinical diagnoses of AD and leaves the field struggling to explain what causes dementia in these amyloid-negative individuals. This promises to be an intense area of investigation, said Reiman.

Articles like these are often difficult for a lay person to understand. But from what I can understand and already know I would say the title is begging the question a tad. It should be no surprise that many people diagnosed with AD are found post mortem not to have amyloid accumulation in their brains. But surely this could be because either, as the title says, people without the amyloid must have a different disease or different diseases OR because, as other research suggests, amyloid accumulation is not as significant in AD as is so often claimed.