dementia—Lewy body type
Definition A neurodegenerative disorder (OMIM:127750) characterised by mental impairment leading to dementia, parkinsonism, fluctuating cognitive function, visual hallucinations, falls, syncopal episodes, and increased sensitivity to neuroleptic medication.
Micro Brainstem or cortical intraneuronal accumulations of aggregated proteins—Lewy bodies are the sine qua non diagnostic features. Enough hippocampal and neocortical senile plaques may be present to fulfil the diagnostic criteria for Alzheimer disease.
Molecular pathology Defects of:
• SNCA, which encodes alpha synuclein, a protein that may be involved in regulating dopamine release and transport, cause dementia—Lewy body type.
• SNCB, which encodes a synuclein that is homologous to alpha-synuclein, highly expressed in the brain and may play a role in neural plasticity by regulating SNCA aggregation, cause dementia—Lewy body type.
• GBA, which encodes a lysosomal membrane protein that cleaves the beta-glucosidic linkage of glycosylceramide, an intermediate in glycolipid metabolism increase the susceptibility to dementia—Lewy body type.