Numerous studies have shown that NFL is a reliable measure of nerve involvement in the presymptomatic stage of central nervous system diseases, including frontotemporal dementia,65 Alzheimer disease,66 multiple sclerosis,67 and ALS.57 To date, the role of blood biomarkers for the early or presymptomatic detection of peripheral neuropathy remains understudied. This evidence concerns the gene NEFL and amyotrophic lateral sclerosis.