Plasma NFL levels are elevated in several neurodegenerative diseases, including amyotrophic lateral sclerosis (Lu et al., 2015), multiple sclerosis (Piehl et al., 2018), Alzheimer’s disease (Weston et al., 2017), and atypical parkinsonian syndromes (Hansson et al., 2017). Here, NEFL is linked to multiple sclerosis.