Researchers at the University of Kentucky have discovered a new type of Alzheimer's disease that could already be affecting tens of thousands.
Called "LATE disease", it has exactly the same symptoms as Alzheimer's, however researchers say it looks completely different on a brain scan.
Which goes some way to explaining why scientists have struggled for so long to find a cure for the brain disease: LATE disease likely requires a very different treatment to Alzheimer's.
Lead author, Dr Peter Nelson, of the Sanders-Brown Center on Ageing at the University of Kentucky, hopes to show that the current "one-size-fits-all" approach to dementia needs to be reconsidered.
"More than 200 different viruses can cause the common cold," said Nelson, "So why would we think there is just one cause of dementia?"
He adds: "LATE probably responds to different treatments than AD, which might help explain why so many past Alzheimer's drugs have failed in clinical trials.
"Now that the scientific community is on the same page about LATE, further research into the 'how' and 'why' can help us develop disease-specific drugs that target the right patients."
LATE affects multiple areas of cognition, and ultimately impairs activities of daily life, however it does appear to progress more gradually.
But when LATE is combined with Alzheimer's - which apparently can be common - it causes a more rapid decline than the disease would on it's own.
Nelson claims the research, published in the journal Brain, is on par with Benjamin Franklin's discovery of electricity.
"People had seen lightning before of course, but Franklin helped formalise a concept that augmented our ability to study electricity," he said.
"By developing a sense of scientific focus around these data, we hope to jump-start a broad field of work to advance our understanding of this form of dementia and, ultimately, to open new opportunities for treatment."