What if part of the challenge of treating Alzheimer’s was because the patient didn’t actually have that disease at all? A team of researchers has described a set of criteria for a neurodegenerative disease that has symptoms quite similar to Alzheimer’s, but does not produce the associated amyloid plaques. This new disease has been dubbed “primary age-related tauopathy (PART).” This new definition could lead to better treatment options in the future. The research was co-led by Peter Nelson of the University of Kentucky's Sanders-Brown Center on Aging, and the paper was published in the journal Acta Neuoropathologica.
"To make an Alzheimer's diagnosis you need to see two things together in a patient's brain: amyloid plaques and structures called neurofibrillary tangles composed of a protein called tau," Nelson said in a press release. "However, autopsy studies have demonstrated that some patients have tangles but no plaques and we've long wondered what condition these patients had.”
Amyloid plaques caused by an accumulation of amyloid-beta proteins are a sure sign of Alzheimer’s disease. When the tau tangles can be seen in patients with Alzheimer’s-like symptoms without the amyloid plaque, the disease was assumed to have been in its early stages. While prior research has shown that incorrectly-folded amyloid-beta proteins can cause tau proteins to misfold, some patients with neurofibrillary tangles have amyloid-beta proteins that are functioning just fine.
Nelson’s team reasoned that if the plaques are the stamp of Alzheimer’s, then patients who have tangles without any plaque likely have something different entirely. These patients would now be categorized as having PART. Because Alzheimer’s treatment focuses on treating amyloid, which isn’t the problem for those with PART, new treatment options will need to be made available before the brain suffers irreversible damage.
"Until now, PART has been difficult to treat or even study because of lack of well-defined criteria," Nelson continued. "Now that the scientific community has come to a consensus on what the key features of PART are, this will help doctors diagnose different forms of memory impairment early. These advancements will have a big impact on our ability to recognize and develop effective treatments for brain diseases seen in older persons.”
Because this definition is so new, it’s not clear how many people have PART. Some studies have found that a quarter of patients with tangles attributed to Alzheimer’s had functional amyloid and would instead be categorized as PART. This new clear criteria for PART will allow doctors and physicians to identify these patients in the future and work toward developing a better treatment that addresses tau instead of amyloid.