NRGN and frontotemporal dementia: Moreover, other studies have shown that Ng could be a disease-specific biomarker as its levels were found to be elevated exclusively in patients with AD, but not in other neurodegenerative disorders, such as FTD, LBD, PD, progressive supranuclear palsy (PSP), or multiple system atrophy (MSA), with the only exception of a speech variant of FTD (svFTD = semantic variant of FTD) [120].