5. Dementia with Lewy bodies (DLB)
The genetics of dementia with Lewy bodies (DLB) are not well understood - there are just not as many research studies as there have been for Alzheimer's disease and frontotemporal dementia. There are a few studies that suggest birth relatives of an affected family member may be at slightly higher risk, but this is not conclusive.
Familial dementia with Lewy bodies
There are only a few known families in which DLB seems to follow a strong inheritance pattern and no mutations have so far been identified.
Risk genes for dementia with Lewy bodies
Several gene variants have recently been linked to a higher risk of DLB. The APOE e4 variant is thought to be the strongest genetic risk factor for DLB, as it is for Alzheimer's disease. Variants in two other genes, glucocerebrosidase (GBA) and alpha-synuclein (SNCA), also affect the risk of a person developing DLB. Alpha-synuclein is the main protein within Lewy bodies, which are found in both DLB and Parkinson's disease. The GBA and SNCA genes are also both important in Parkinson's disease.
It is not surprising that the gene variants associated with DLB also play a role in Alzheimer's disease (APOE) and Parkinson's disease (GBA, SNCA). This is because the symptoms of DLB overlap with those of both Alzheimer's disease and Parkinson's, and the diseases share some common underlying features.