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Condition report · Neurological

Lewy Body Dementia

Whole genome sequencing reads GBA1, APOE and SNCA, genes linked to the risk of Lewy body dementia, a form of dementia caused by abnormal deposits in the brain.

A condition report looks for rare variants known to cause the conditions it covers.

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About this condition

Lewy body dementia is a form of dementia in which abnormal deposits called Lewy bodies build up in the brain. GBA1 (also called GBA), APOE and SNCA are the genes with the clearest links to risk, but most risk is not explained by these genes.

Lewy body dementia is the name for dementia in which abnormal deposits called Lewy bodies build up in brain cells. Researchers describe dementia with Lewy bodies as the second most common form of dementia in older people. Its symptoms can overlap with Alzheimer's disease and Parkinson's disease, which makes it easy to misdiagnose.

Most people with the condition do not have a single gene change that causes it. In a large genome sequencing study, researchers found five independent risk loci, and gene-level tests pointed to GBA1. Studies have also found links with APOE and SNCA. These genes raise or lower risk. They do not on their own decide whether someone develops the condition.

A genetic result can add to the picture, but it is not a diagnosis. Diagnosis depends on the clinical features, assessed by a specialist, using international consensus criteria.

The condition we analyse

Most cases are not inherited in a simple way. The main known genetic risk factors are changes in GBA1 (also called GBA), the APOE e4 allele and variation near SNCA, each of which changes the chance of developing the condition rather than causing it outright.

Signs and symptoms

Core features include fluctuating attention and alertness, recurrent visual hallucinations (seeing things that are not there), parkinsonism (slowness, stiffness and shaking, as in Parkinson's disease) and REM sleep behaviour disorder, in which a person acts out their dreams during sleep. Sleep disturbance is also common.

What a diagnosis changes

Diagnosis rests on the core features and specialist assessment. Doctors should be careful with antipsychotic medicines, because severe reactions occurred in about half of the people with Lewy body dementia in one study. Wider care is mostly based on expert opinion.

Genes analysed

Also known as

cortical Lewy body disease; dementia with Lewy bodies; DLB; lewy body dementia, susceptibility to; Lewy body disease

MONDO:0007488OMIM 127750Orphanet 1648MedGen 199874Sources: [1][2][3][4][5][6][7]

Why whole genome sequencing

Lewy body dementia is mostly not inherited in a simple way, so a gene result gives only part of the picture.

Several genes add to risk

GBA1, APOE and SNCA are the genes with the clearest links to Lewy body dementia. Whole genome sequencing reads them in the same test.

Most risk is not explained by these genes

One large study estimated that about 36% of the risk is heritable, and the known risk loci explain only part of that. A result does not show whether someone will develop the condition.

Medicines need care

Severe reactions to antipsychotic medicines occurred in about half of the people with Lewy body dementia in one study, so specialists usually take care with these medicines.

Limitations

  • Most of the risk for Lewy body dementia is not explained by GBA1, APOE or SNCA. One large study estimated the heritable part at about 36%, and the risk loci found so far account for only some of it.
  • A change in GBA1, APOE or SNCA changes the chance of developing the condition. It does not mean a person will develop it, and not having one does not rule it out.
  • Changes in other genes, and other causes of dementia, are not covered by this report.

References

  1. Chia R, Sabir MS, Bandres-Ciga S, Saez-Atienzar S, Reynolds RH, Gustavsson E et al., 2021. Genome sequencing analysis identifies new loci associated with Lewy body dementia and provides insights into its genetic architecture
  2. Guerreiro R, Ross OA, Kun-Rodrigues C, Hernandez DG, Orme T, Eicher JD et al., 2018. Investigating the genetic architecture of dementia with Lewy bodies: a two-stage genome-wide association study
  3. Orme T, Guerreiro R, Bras J, 2018. The Genetics of Dementia with Lewy Bodies: Current Understanding and Future Directions
  4. Matar E, White SR, Taylor JP, Thomas A, McKeith IG, Kane JPM et al., 2021. Progression of Clinical Features in Lewy Body Dementia Can Be Detected Over 6 Months
  5. Tousi B, 2017. Diagnosis and Management of Cognitive and Behavioral Changes in Dementia With Lewy Bodies
  6. McKeith IG, Boeve BF, Dickson DW, Halliday G, Taylor JP, Weintraub D et al., 2017. Diagnosis and management of dementia with Lewy bodies: Fourth consensus report of the DLB Consortium
  7. Aarsland D, Perry R, Larsen JP, McKeith IG, O'Brien JT, Perry EK et al., 2005. Neuroleptic sensitivity in Parkinson's disease and parkinsonian dementias

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