FTD patients had a higher mean serum NfL concentration compared to PPD and controls (FTD 29.3 ± 18.0 pg/ml versus PPD 9.5 ± 2.8 pg/ml versus controls 8.9 ± 4.3 pg/ml, P < 0.001, adjusted for age, sex and GDS, explained variance 61%, Fig. 2). Here, NEFL is linked to frontotemporal dementia.