Frontal lobe dementia (Frontotemporal Dementia, FTD) strikes people at an earlier age. After Alzheimer's disease, FTD is the form of dementia that occurs most frequently in patients younger than 65.
In FTD, the disease process starts in the frontal lobe where large numbers of brain cells begin to die off. The frontal lobe is the foremost part of the brain and constitutes about 30% of the brain. Among other things, it is involved in regulating behavior, movement and mood, and it is responsible for cognitive functions such as language. So, the first clinical signs of FTD are changes in behavior and personality, and then, in a later stage of the disease, the loss of memory functions.
Progranulin: a main actor
Genetic research has shown previously that there is a genetic defect in chromosome 17 in a large percentage of the families with FTD. There are two genes in chromosome 17 that, if a defect occurs, cause a hereditable form of FTD. In 1998, defects were found in the gene for the tau protein, a substance that appears in the protein clots in the brains of FTD and Alzheimer's patients. In 2006, Christine Van Broeckhoven's team discovered hereditable defects in the gene for the progranulin protein. They predicted that people with these hereditable defects produce only half of the normal amount of progranulin.