Isolated increase in CSF total tau with no reduction in CSF amyloid-β42 is supportive of a diagnosis of bvFTD, since CSF amyloid-β42 in definite bvFTD was found to be normal, while CSF total tau levels are commonly increased, as a marker of neurodegeneration41,.42 This evidence concerns the gene MAPT and behavioral variant of frontotemporal dementia.