The terms Alzheimer's disease (AD), Parkinson's disease (PD), PD dementia (PDD) and dementia with Lewy bodies (DLB) are used by clinicians to describe the pattern and chronology of clinical presentations, the discrimination of which is useful for patient diagnosis and management. The term LB disease is used by clinicians to refer to the PD/PDD/DLB spectrum and by clinicians and scientists to refer to a pathological disease process.
A series of targeted workshops on DLB and PD dementia has led to the acceptance of operationalised criteria for the clinical diagnosis of DLB and PDD that are mutually compatible and consistent with similar systems for AD and PD. Precise use of terminology and theoretical frameworks is important to ensure that these carefully agreed categorical entities are used correctly. If not, the interpretation and comparison of translational research and clinical trials in the LB disease spectrum becomes confounded. Conversely, when considered collectively using a broad spectrum model the combined categories may capture sufficient heterogeneity to render clinicopathological correlative studies more meaningful and will allow the development and trialling of disease modifying agents for LB disorders that can be interpreted more widely than is currently the case.
Formulation of pathological criteria for LB disorders has been more problematic because of the variable pattern of expression of neuropathological lesions (τ, amyloid and α-synuclein based abnormalities) which correlate only to a limited degree with clinical phenotype, disease severity and progression.