Evidence of increased NfL levels in ALS/MND, which is most commonly a TDP-43 proteinopathy [42–44], and in the semantic variant primary progressive aphasia [9,10], which also most commonly characterized by misfolding of TDP-43 [45], suggest a link between NfL and TDP-43 proteinopathy in the FTD spectrum [10]. This evidence concerns the gene NEFL and amyotrophic lateral sclerosis.