CSF NfL was reported recently to have a diagnostic potential even for presymptomatic ALS.18 However, at present, it is not possible to predict which kind of neurodegeneration will develop in individuals with elevated CSF NfL levels due to its lack of disease specificity.24 The combined use of CSF NfL and CSF TDP‐43 may be recommended for such people suspected to have neurodegeneration with undetermined pathology. This evidence concerns the gene NEFL and amyotrophic lateral sclerosis.