Dementia with Lewy bodies is a neurodegenerative disorder resulting in progressive cognitive decline and parkinsonism. Cognitive impairment occurs before or within 1 year of parkinsonism. The disease is age-related, with variable age of onset often between age 50 and 85. It is more common in men.

Core clinical features include dementia, parkinsonism (bradykinesia, rigidity, tremor), fluctuating levels of alertness and cognition, visual hallucinations, and rapid eye movement (REM) sleep behavior disorder (dream enactment).

Additional features include frequent falls, orthostatic hypotension, constipation, urinary incontinence, neuroleptic sensitivity, myoclonus, depression, anxiety, apathy, systematized delusions, hypersomnia, and hyposmia.

Lack of response to levodopa is common; sustained dramatic positive response to levodopa should bring the diagnosis into question. Prognosis is poor, and most patients are significantly disabled within 5 years of diagnosis and die within 10 years of diagnosis.

Patients with this disorder may have an increased risk of various general medical conditions.