There is a growing awareness that dementia can be due to a variety of different cases, although some pathways appear to be related. Frontotemporal dementia (FTD), semantic dementia (SD) and progressive nonfluent aphasia (PNFA) are all due to the progressive loss of neurons in the frontal and/or temporal lobes. This group of disorders is often referred to as frontotemporal lobar degeneration (FTLD).
Several genes have been identified which when mutated can result in FTLD. The first to be identified was the microtubule associated protein tau (MAPT). Mutations in this gene are found in about 5-10% of FTLD patients. Subsequently, a second gene was identified. Mutations in progranulin (GRN), can also result in FTLD. GRN mutations are found in another 5-10% of FTLD patients. In rare cases, mutations in two other genes, VCP and CHMP2B can also cause FTLD. Mutations in these 4 genes are most common in familial cases of FTLD; that is families in which there are multiple members with the disease. Most recently, mutations were identified in C9ORF72 that contribute to both familial FTD and familial ALS.
Studies using samples collected and distributed by the National Cell Repository for Alzheimer's Disease will help scientists identify the other important genes contributing to non-AD dementia.
For more information about genetics, please see the Alzheimer's Disease Genetics Fact Sheet from the Alzheimer’s Disease Education & Referral Center (ADEAR) website.