The terms dementia and Alzheimer’s are used interchangeably, but Alzheimer’s is actually just one type of dementia. Dementia is an umbrella term for a number of diseases, all of which include symptoms of severe memory loss, difficulty communicating and decline of reasoning abilities. While Alzheimer’s, defined by the presence of toxic protein plaques in the brain, accounts for 60 to 80 percent of dementia cases, there are many types of dementia. Getting the right diagnosis has become more important than ever, as scientists are realizing that each type of dementia has unique causes and needs a different approach to drug treatment.
That was demonstrated in a new study that found that Lewy body dementia (LBD), a type of dementia characterized by deposits of a protein called alpha-synuclein in the brain, has a unique genetic profile, distinct from other types of dementia like Parkinson’s and Alzheimer’s.
“Dementia with Lewy bodies is often misunderstood as being a mixture of Alzheimer’s and Parkinson’s, but this confirms it’s actually a unique condition,” said Doug Brown, Ph.D., director of research at Alzheimer’s Society, which funded the study.
Researchers at University College London looked at over 1,700 people with Lewy body dementia. They found that some of the same genes associated with Alzheimer’s are associated with LBD, but others were not, or a different part of the gene was linked to LBD. They also estimated how likely it is that children of someone with LBD might also get the disease.
“Despite LBD being one of the most common forms of dementia in older people, until now there simply hasn’t been enough information on its causes, so the finding that up to 36 percent of cases might be genetically inherited is a real revelation,” said Brown.
Patients with LBD don’t have as much trouble with short-term memory as Alzheimer’s patients, but they deteriorate more rapidly and patients experience paranoia and hallucinations along with failing executive function. It’s the disease actor Robin Williams was diagnosed with after his death. A large study last year showed that a third of Alzheimer’s patients are misdiagnosed—and often, they have Lewy body dementia or another type of dementia.
“Dementia with Lewy bodies accounts for 10 to 15 percent of dementia cases, yet our understanding of it lags beyond the more well-known Alzheimer’s disease, partly because it’s commonly misdiagnosed,” said senior study investigator Jose Bras, Ph.D., a UCL Institute of Neurology and Alzheimer’s Society senior research fellow. “Our findings clarify the disease’s distinctive genetic signature, which should, in the future, help improve clinical trials and lead to more targeted treatments.”
This study was published in the journal The Lancet Neurology.