Dementia with Lewy bodies (DLB) is one of the most common types of progressive dementia. The central feature of DLB is progressive cognitive decline, which is combined with pronounced "fluctuations" in alertness and attention, such as frequent drowsiness, lethargy, lengthy periods of time spent staring into space, and disorganized speech; recurrent visual hallucinations; and parkinsonian motor symptoms, such as rigidity and the loss of spontaneous movement. People may also suffer from depression. The symptoms of DLB are caused by the buildup of Lewy bodies-accumulated bits of alpha-synuclein protein-inside the nuclei of neurons in areas of the brain that control particular aspects of memory and motor control. Researchers don't know exactly why alpha-synuclein accumulates into Lewy bodies or how Lewy bodies cause the symptoms of DLB, but they do know that alpha-synuclein accumulation is also linked to Parkinson's disease, multiple system atrophy, and several other disorders referred to as the "synucleinopathies." The similarity between the symptoms of DLB and Parkinson's disease and of DLB and Alzheimer's disease can often make it difficult for a doctor to make a definitive diagnosis. In addition, Lewy bodies are often also found in the brains of people with Parkinson's and Alzheimer's diseases. These findings suggest that either DLB is related to these other causes of dementia or that an individual can have both diseases at the same time. DLB usually occurs sporadically, in people with no known family history of the disease. However, rare familial cases have occasionally been reported.
This information is based on source information from the National Institute of Neurological Disorders and Stroke.