Interestingly, it has been recently described that CSF progranulin but not serum/plasma progranulin, is reduced also in GRN-negative FTD (Wilke et al., 2017): this reduction seems extend beyond the recognized modification of CSF progranulin levels by the SNP rs5848 (Nicholson et al., 2014) and it is not directly linked to tau alterations. The gene discussed is MAPT; the disease is frontotemporal dementia.