Lewy body dementias (LBDs, or Lewy body disorders) describe two similar common dementias that are characterized by changes in thinking, movement, behavior, and mood. They are dementia with Lewy bodies (DLB), and
Parkinson's disease dementia (PDD).Lewy body dementia is an umbrella term encompassing the two conditions. The two conditions have similar features and may have similar causes, and are believed to belong on a spectrum of Lewy body disease that includes Parkinson's disease. As of 2014, they were more often misdiagnosed than any other common dementia. The exact cause is unknown, but involves widespread deposits of abnormal clumps of protein that form in neurons of the diseased brain. Known as Lewy bodies (discovered in 1912 by Frederic Lewy) and Lewy neurites, these clumps affect both the central nervous system and the autonomic nervous system.