In addition, elevated levels of TDP-43 has been found in the cerebrospinal fluid35–37 as well as in plasma of ALS38–40, FTD and Alzheimer41,42 patients, and in FTD patients carrying C9orf72 expansion or GRN mutations, plasma phosphorylated TDP-43 levels have been found to be higher than in healthy controls43. Here, GRN is linked to frontotemporal dementia.