NEFL and amyotrophic lateral sclerosis: Longitudinal data from the Genetic FTD Initiative (GENFI; www.genfi.org) and Advancing Research and Treatment for Frontotemporal Lobar Degeneration/Longitudinal Evaluation of Familial FrontoTemporal Dementia Subjects (ALLFTD; www.allftd.org) networks,3,4 as well as a network of French amyotrophic lateral sclerosis (ALS) and FTD clinics,5 suggest that NfL may be a valuable blood-based biomarker, reporting that NfL baseline levels and rate of change with disease progression differ among the FTLD gene mutation subtypes as compared with healthy controls.